{ "modality": "MRI", "exam_facts": { "scored_questions": 200, "pilot_questions": 30, "time_limit_minutes": 230, "spec_version": "Effective February 1, 2025 (ARRT Board approved January 2024). ARRT has posted a revised MRI specification effective February 1, 2028 (board approval pending) that changes the counts to Patient Care 20, Safety 40, Image Production 86, and Procedures 54.", "source_url": "https://assets-us-01.kc-usercontent.com/406ac8c6-58e8-00b3-e3c1-0c312965deb2/8a6d78b2-c8bf-4a57-b824-85a9bc5a98e5/Magnetic%20Resonance%20Imaging%20Content%20Specifications%202025.pdf" }, "content_categories": [ { "name": "Patient Care", "scored_questions": 16, "subcategories": [ { "name": "Patient Interactions and Management", "scored_questions": 16 } ] }, { "name": "Safety", "scored_questions": 21, "subcategories": [ { "name": "MRI Screening and Safety", "scored_questions": 21 } ] }, { "name": "Image Production", "scored_questions": 106, "subcategories": [ { "name": "Physical Principles of Image Formation", "scored_questions": 40 }, { "name": "Sequence Parameters and Options", "scored_questions": 36 }, { "name": "Data Acquisition, Processing, and Storage", "scored_questions": 30 } ] }, { "name": "Procedures", "scored_questions": 57, "subcategories": [ { "name": "Neurological", "scored_questions": 25 }, { "name": "Body", "scored_questions": 15 }, { "name": "Musculoskeletal", "scored_questions": 17 } ] } ], "sections": [ { "id": "patient-care", "name": "Patient Care", "main_points": [ "Verify identity with at least two identifiers, confirm the order matches the clinical indication, and perform a time-out before invasive steps such as an arthrogram injection.", "Informed consent requires a competent patient who understands the purpose, risks, benefits, and alternatives; consent may be written, oral, or implied (e.g., in an emergency).", "Know the legal vocabulary: battery is touching without consent, negligence is failure to meet the standard of care, respondeat superior makes the employer liable for employees, and res ipsa loquitur means 'the thing speaks for itself.'", "Gadolinium-based contrast agents (GBCAs) are paramagnetic and shorten T1 (and T2) of nearby protons, so enhancing tissue becomes bright on T1-weighted images.", "Macrocyclic GBCAs hold gadolinium more tightly than linear agents, lowering the risk of free-gadolinium release, brain deposition, and nephrogenic systemic fibrosis (NSF).", "Screen renal function (eGFR, creatinine, BUN) for at-risk patients; severe kidney disease (eGFR below 30 mL/min/1.73 m², or dialysis) is the main NSF risk factor.", "Contrast reactions range from mild (limited hives, nausea) to moderate and severe (bronchospasm, laryngeal edema, hypotension); know where emergency drugs such as epinephrine are and document every reaction.", "During a cardiac or respiratory arrest, start CPR and move the patient out of Zone IV for resuscitation; never bring an unscreened crash cart or code team into the magnet room.", "For extravasation, stop the injection, elevate the limb, apply a compress per protocol, notify the radiologist, and document the event.", "Power injectors and timing methods (test/timing bolus, automatic bolus tracking, fluoro-triggering) synchronize contrast arrival with acquisition, especially for MRA and dynamic studies.", "Apply Standard Precautions to every patient and add contact, droplet, or airborne precautions by pathogen; clean coils and table pads between patients.", "Reduce claustrophobia with clear explanation, feet-first positioning when the exam allows, prism glasses or a mirror, a family member in the room (if screened), and sedation per order with MR Conditional monitoring." ], "vocabulary": [ { "term": "Informed consent", "definition": "A patient's voluntary agreement to a procedure after being told its purpose, risks, benefits, and alternatives." }, { "term": "Battery", "definition": "Intentional touching or treating of a patient without consent." }, { "term": "Negligence", "definition": "Failure to provide the care a reasonable professional would provide under similar circumstances." }, { "term": "Respondeat superior", "definition": "Legal doctrine ('let the master answer') holding an employer liable for the acts of its employees on the job." }, { "term": "Res ipsa loquitur", "definition": "Doctrine ('the thing speaks for itself') used when an injury could only have resulted from negligence." }, { "term": "Gadolinium-based contrast agent (GBCA)", "definition": "A paramagnetic MR contrast agent that shortens T1 relaxation, brightening enhancing tissue on T1-weighted images." }, { "term": "Macrocyclic agent", "definition": "A GBCA whose cage-like ligand binds gadolinium tightly, making it more stable than a linear agent." }, { "term": "Nephrogenic systemic fibrosis (NSF)", "definition": "A rare fibrosing disease of skin and organs linked to GBCA exposure in patients with severe renal impairment." }, { "term": "eGFR", "definition": "Estimated glomerular filtration rate, a calculated measure of kidney function used to screen before contrast." }, { "term": "Extravasation", "definition": "Leakage of injected contrast or fluid from the vein into surrounding soft tissue." }, { "term": "Time-out", "definition": "A pause just before an invasive procedure to confirm the correct patient, procedure, and site." }, { "term": "Bolus tracking", "definition": "Real-time monitoring of contrast arrival in a target vessel to trigger the scan automatically or manually." }, { "term": "Standard Precautions", "definition": "CDC infection-control practices (hand hygiene, PPE, safe injection, cleaning) used with every patient." }, { "term": "Airborne precautions", "definition": "Transmission-based precautions for pathogens such as TB that require an N95 respirator and a negative-pressure room." }, { "term": "Fomite", "definition": "An inanimate object, such as a coil or table pad, that can carry infectious organisms." }, { "term": "Neutropenic precautions", "definition": "Reverse isolation that protects an immunocompromised patient from the environment and staff." } ], "quiz": [ { "q": "A hospital is sued because a technologist it employs injured a patient through carelessness. Which legal doctrine makes the hospital answerable?", "options": [ "Res ipsa loquitur", "Stare decisis", "Respondeat superior", "Primum non nocere" ], "answer_index": 2, "explanation": "Respondeat superior holds an employer liable for the actions of employees performed within the scope of their job." }, { "q": "How does a gadolinium-based contrast agent increase signal in enhancing tissue on T1-weighted images?", "options": [ "It shortens the T1 relaxation time of nearby hydrogen protons", "It lengthens the T2 relaxation time of nearby protons", "It increases the proton density of the tissue", "It blocks the RF pulse from reaching surrounding tissue" ], "answer_index": 0, "explanation": "Gadolinium is paramagnetic; it speeds T1 recovery of neighboring protons so they return more signal on T1-weighted sequences." }, { "q": "Which laboratory result raises the greatest concern for nephrogenic systemic fibrosis before a gadolinium injection?", "options": [ "eGFR of 95 mL/min/1.73 m²", "eGFR of 75 mL/min/1.73 m²", "Creatinine of 0.9 mg/dL", "eGFR of 25 mL/min/1.73 m²" ], "answer_index": 3, "explanation": "Severe renal impairment (eGFR below 30) is the main risk factor for NSF; the other values are normal or near normal." }, { "q": "An outpatient in the scanner develops a few hives and mild itching after gadolinium. How is this reaction classified?", "options": [ "Moderate", "Mild", "Severe", "Life-threatening" ], "answer_index": 1, "explanation": "Limited urticaria and pruritus without other symptoms are classic mild reactions; still monitor the patient and notify the radiologist." }, { "q": "A patient in Zone IV becomes unresponsive and pulseless. What is the most appropriate action?", "options": [ "Call the code team and crash cart directly into the magnet room", "Begin CPR and move the patient out of Zone IV to a safe area for the code team", "Quench the magnet before touching the patient", "Finish the current sequence, then assess the patient" ], "answer_index": 1, "explanation": "Resuscitation equipment and responders are usually not MR safe, so the patient is moved out of Zone IV while basic life support continues." }, { "q": "During a power injection, the IV site swells and the patient reports pain. What should the technologist do first?", "options": [ "Continue at a slower flow rate", "Flush the line with saline at high pressure", "Apply a tight tourniquet above the site", "Stop the injection and notify the radiologist" ], "answer_index": 3, "explanation": "Stopping the injection limits the extravasated volume; elevation, a compress per protocol, and documentation follow." }, { "q": "A patient with suspected active pulmonary tuberculosis needs an MRI. Which transmission-based precautions apply?", "options": [ "Airborne", "Contact", "Droplet", "Neutropenic" ], "answer_index": 0, "explanation": "TB spreads by small airborne particles, requiring an N95 respirator for staff and a mask on the patient during transport." }, { "q": "When is a procedural time-out performed for an MR arthrogram?", "options": [ "After the MR images are sent to PACS", "When the patient is scheduled", "Immediately before the joint injection begins", "Only if the patient asks questions" ], "answer_index": 2, "explanation": "The time-out happens just before the invasive step to confirm the correct patient, procedure, and side." }, { "q": "A claustrophobic patient is scheduled for a knee MRI. Which nonpharmacologic strategy is most likely to help?", "options": [ "Use soft restraints so the patient cannot move", "Turn off the bore fan and lights to reduce stimulation", "Avoid explaining the exam so the patient is not worried", "Position the patient feet-first so the head remains near or outside the bore" ], "answer_index": 3, "explanation": "Feet-first entry for lower-extremity exams keeps the head out of the bore, which greatly reduces anxiety." }, { "q": "A technologist starts an IV after the patient clearly says, 'I do not want an injection.' This act is best described as:", "options": [ "Libel", "Battery", "Slander", "Invasion of privacy" ], "answer_index": 1, "explanation": "Touching a patient after consent is refused is battery; libel and slander concern false written or spoken statements." }, { "q": "Which device is appropriate for monitoring a sedated patient's oxygen saturation during an MRI scan?", "options": [ "A standard ICU monitor brought into Zone IV", "No monitoring, since the patient is asleep", "An MR Conditional pulse oximeter used within its labeled conditions", "A standard pulse oximeter with its cable coiled on the patient" ], "answer_index": 2, "explanation": "Sedated patients need continuous monitoring with equipment tested for the MR environment; coiled cables can cause burns." }, { "q": "Which contrast-timing method watches a target vessel in real time and starts acquisition when contrast arrives?", "options": [ "Automatic bolus tracking", "Fixed empirical delay", "Gradient moment nulling", "Delayed hepatobiliary imaging" ], "answer_index": 0, "explanation": "Bolus tracking (or fluoro-triggering) monitors signal in a region of interest and triggers the scan on contrast arrival." } ], "bank": [ { "q": "A patient in her first trimester needs a non-contrast MRI for suspected appendicitis. What is the most appropriate approach?", "options": [ "Postpone until the second trimester, because MRI is contraindicated in the first trimester", "Use a 3 T scanner so the exam is shorter and the fetal dose is lower", "Scan only after the patient signs a waiver accepting the risk of ionizing radiation", "Proceed when the referring and supervising physicians agree the benefit justifies the exam; non-contrast MRI may be done at any stage of pregnancy" ], "answer_index": 3, "explanation": "ACR guidance permits non-contrast MRI at any stage of pregnancy when the clinical benefit warrants it; MRI uses no ionizing radiation.", "subcategory": "Patient Interactions and Management" }, { "q": "A breastfeeding mother asks whether she must stop nursing after a gadolinium-enhanced MRI. What does current ACR guidance say?", "options": [ "She may continue breastfeeding without interruption; pausing for 12-24 hours is an optional personal choice", "She must stop breastfeeding for one week", "Gadolinium is contraindicated in breastfeeding patients", "She must pump and discard milk for 48 hours" ], "answer_index": 0, "explanation": "Less than 0.04% of the gadolinium dose reaches breast milk, so ACR advises no interruption; a temporary pause is left to the mother's preference.", "subcategory": "Patient Interactions and Management" }, { "q": "An outpatient with a prior moderate allergic-like reaction to gadolinium is scheduled for an elective contrast MRI. Which premedication regimen is a standard ACR elective option?", "options": [ "Hydration with 1 L of normal saline the night before", "Prednisone 50 mg orally at 13, 7, and 1 hour before injection, plus diphenhydramine 50 mg 1 hour before", "Diphenhydramine 50 mg orally 15 minutes before injection only", "Epinephrine 0.3 mg IM 1 hour before injection" ], "answer_index": 1, "explanation": "The 13-hour oral prednisone regimen with diphenhydramine 1 hour before is a standard ACR elective premedication schedule.", "subcategory": "Patient Interactions and Management" }, { "q": "Minutes after gadolinium injection, a patient develops throat tightness, wheezing, and a blood pressure of 78/40 mm Hg. Which medication is first-line?", "options": [ "Intramuscular epinephrine (1 mg/mL concentration)", "Oral diphenhydramine", "Oral prednisone", "Intravenous atropine" ], "answer_index": 0, "explanation": "Anaphylaxis with airway involvement and hypotension is a severe reaction; IM epinephrine is the first-line drug while the emergency team is called.", "subcategory": "Patient Interactions and Management" }, { "q": "After an IV start, a patient becomes pale and sweaty, with a pulse of 45 bpm and blood pressure of 80/50 mm Hg. Which response fits this vasovagal reaction?", "options": [ "Place the patient upright with head elevated to 90 degrees", "Elevate the legs, give oxygen, and start IV fluids; atropine may be given if bradycardia persists", "Give IM epinephrine immediately", "Give an oral antihistamine and continue the scan" ], "answer_index": 1, "explanation": "A vasovagal reaction combines bradycardia and hypotension; leg elevation, oxygen, and IV fluids are first steps, with atropine for persistent bradycardia.", "subcategory": "Patient Interactions and Management" }, { "q": "Which pair is acceptable for verifying patient identity before an MRI?", "options": [ "The bed number and the ordering physician", "The patient's name and room number", "The wristband color and the exam type", "The patient's full name and date of birth" ], "answer_index": 3, "explanation": "Joint Commission safety goals require two person-specific identifiers; a room or bed number is not acceptable.", "subcategory": "Patient Interactions and Management" }, { "q": "An 80-kg patient is to receive a gadolinium agent at 0.1 mmol/kg. The agent's concentration is 0.5 mmol/mL. What volume is injected?", "options": [ "8 mL", "32 mL", "16 mL", "20 mL" ], "answer_index": 2, "explanation": "Dose = 80 kg x 0.1 mmol/kg = 8 mmol; 8 mmol / 0.5 mmol/mL = 16 mL.", "subcategory": "Patient Interactions and Management" }, { "q": "During an exam under moderate sedation, a pediatric patient's oxygen saturation drops from 98% to 86%. What should the technologist do first?", "options": [ "Increase the scanner's room ventilation fan speed", "Stop the scan, assess the patient's airway and breathing, and alert the supervising nurse or physician", "Reposition the pulse oximeter probe and keep scanning", "Finish the current sequence, then check the patient" ], "answer_index": 1, "explanation": "A falling SpO2 in a sedated patient may signal airway compromise; the patient takes priority over completing the sequence.", "subcategory": "Patient Interactions and Management" }, { "q": "Who is responsible for obtaining informed consent before an MR arthrogram injection?", "options": [ "The front-desk scheduler", "The MR technologist who will scan the joint", "The physician (or qualified practitioner) performing the injection", "The referring physician's office staff" ], "answer_index": 2, "explanation": "Informed consent must come from the practitioner performing the procedure, who can explain its risks, benefits, and alternatives.", "subcategory": "Patient Interactions and Management" }, { "q": "Two technologists discuss a patient's MRI findings, using the patient's name, in a crowded hospital elevator. This is primarily a breach of:", "options": [ "Patient confidentiality under HIPAA", "Informed consent", "Standard precautions", "The scope of practice for radiologists" ], "answer_index": 0, "explanation": "HIPAA protects identifiable health information; discussing it where others can overhear is an improper disclosure.", "subcategory": "Patient Interactions and Management" }, { "q": "A patient on chronic hemodialysis needs a contrast-enhanced MRI. Which gadolinium agent choice best follows ACR guidance?", "options": [ "A group III agent, because it clears through the bowel instead", "A group I linear agent at a double dose to ensure enhancement", "A group II agent, given at the lowest dose that gives a diagnostic exam", "Any agent, since dialysis fully removes NSF risk immediately" ], "answer_index": 2, "explanation": "ACR group II agents carry the lowest reported NSF risk and are preferred, at the lowest diagnostic dose, for patients on dialysis or with severe kidney disease.", "subcategory": "Patient Interactions and Management" }, { "q": "A patient on contact precautions for Clostridioides difficile has just left the MRI suite. How should the technologist clean their hands?", "options": [ "Wipe hands with the same disinfectant cloth used on the table", "Wash with soap and running water, because alcohol does not kill C. difficile spores", "No hand hygiene is needed if gloves were worn the whole time", "Use an alcohol-based hand rub, which is preferred for all organisms" ], "answer_index": 1, "explanation": "C. difficile spores resist alcohol, so soap-and-water handwashing (and a sporicidal agent for surfaces) is required after glove removal.", "subcategory": "Patient Interactions and Management" }, { "q": "An inpatient with confirmed influenza is brought for a brain MRI. Which precautions should staff follow?", "options": [ "Droplet precautions, including a surgical mask within close range of the patient", "Airborne precautions with a negative-pressure room and N95 respirator", "Contact precautions only, with gown and gloves but no mask", "Standard precautions only, since influenza does not spread in imaging" ], "answer_index": 0, "explanation": "Influenza spreads mainly by large respiratory droplets, so droplet precautions with a surgical mask apply, on top of standard precautions.", "subcategory": "Patient Interactions and Management" }, { "q": "A patient asks about gadolinium retention in the brain after several prior MRIs. Which statement is accurate?", "options": [ "Macrocyclic agents leave more gadolinium in the brain than linear agents", "Retention has been seen mainly in the dentate nucleus and globus pallidus, more with linear than macrocyclic agents", "Retention occurs only in patients with severe kidney failure", "Retention has been proven to cause progressive dementia" ], "answer_index": 1, "explanation": "Signal increase from retained gadolinium is seen mostly in the dentate nucleus and globus pallidus and is greater with less stable linear agents; no clinical harm has been established.", "subcategory": "Patient Interactions and Management" }, { "q": "A patient with right-sided weakness after a stroke must move from a wheelchair to the MR table. Which technique is safest?", "options": [ "Position the chair so the patient moves toward their weaker right side", "Lock the wheels and position the chair so the patient moves toward their stronger left side", "Leave the wheels unlocked so the chair can roll with the patient", "Lift the patient by the arms so the patient does not have to stand" ], "answer_index": 1, "explanation": "Locking the wheels and transferring toward the patient's stronger side lets the patient bear weight and help, which lowers the risk of a fall.", "subcategory": "Patient Interactions and Management" }, { "q": "A diabetic outpatient who skipped breakfast becomes shaky, sweaty, and confused but is awake and able to swallow. What is the most appropriate first action?", "options": [ "Stop the scan, check glucose if possible, and give a fast-acting oral sugar such as juice", "Give the patient an extra dose of their own insulin from their bag", "Continue scanning, since the symptoms are probably caused by anxiety", "Have the patient lie flat and give nothing by mouth until a physician arrives" ], "answer_index": 0, "explanation": "These are signs of hypoglycemia; a conscious patient who can swallow should get fast-acting oral glucose while help is notified.", "subcategory": "Patient Interactions and Management" }, { "q": "A patient begins a generalized tonic-clonic seizure on the MR table. What should the technologist do?", "options": [ "Put a bite block in the mouth to keep the patient from biting the tongue", "Keep scanning so the seizure activity can be captured on the images", "Remove the patient from the bore, protect from injury, and turn onto the side when possible", "Hold the patient's arms and legs firmly to stop the movements" ], "answer_index": 2, "explanation": "During a seizure, protect the patient from injury and keep the airway clear by turning them onto the side; never restrain them or put anything in the mouth.", "subcategory": "Patient Interactions and Management" }, { "q": "A 3-week-old infant needs a non-contrast brain MRI, and the team would like to avoid sedation. Which approach is most commonly used?", "options": [ "Have a parent hold the infant's head still inside the bore", "Scan with a large FOV and few slices so motion does not matter", "Feed the infant, swaddle snugly, and scan once the infant falls asleep", "Give the infant a full adult dose of oral anxiolytic" ], "answer_index": 2, "explanation": "The feed-and-wrap technique uses natural sleep after feeding and swaddling, and often allows neonatal MRI without sedation.", "subcategory": "Patient Interactions and Management" }, { "q": "A patient who speaks only Haitian Creole arrives with an 11-year-old child who offers to interpret the screening form. What is the best practice?", "options": [ "Skip the screening form and rely only on the ferromagnetic detector", "Let the child interpret, since a family member is most trusted", "Have the patient sign the English form and go ahead with scanning", "Use a qualified medical interpreter, in person or by phone or video" ], "answer_index": 3, "explanation": "Accurate MR safety screening and consent need a qualified medical interpreter; children and untrained family members should not interpret clinical information.", "subcategory": "Patient Interactions and Management" }, { "q": "Halfway through a lumbar spine exam, a competent adult says they want to stop and leave. What should the technologist do?", "options": [ "Encourage the patient to finish, since only two sequences remain", "Ask a family member to give consent so the exam can continue", "Finish the current sequence before acknowledging the request", "Stop the exam, remove the patient from the scanner, notify the radiologist, and document the refusal" ], "answer_index": 3, "explanation": "A competent patient may withdraw consent at any time; continuing could be battery, so stop, inform the radiologist, and document.", "subcategory": "Patient Interactions and Management" }, { "q": "What is the normal resting heart rate range for a healthy adult?", "options": [ "12 to 20 beats per minute", "40 to 60 beats per minute", "100 to 140 beats per minute", "60 to 100 beats per minute" ], "answer_index": 3, "explanation": "A normal adult resting pulse is 60 to 100 bpm; below 60 is bradycardia and above 100 is tachycardia.", "subcategory": "Patient Interactions and Management" }, { "q": "A patient taking metformin with normal kidney function is scheduled for a gadolinium-enhanced liver MRI. What does current ACR guidance recommend regarding metformin?", "options": [ "Hold metformin for 24 hours before and 48 hours after the scan", "Hold metformin for 48 hours after the gadolinium injection", "Give the gadolinium only after a repeat creatinine 48 hours later", "No change is needed; metformin does not have to be stopped for a standard GBCA dose" ], "answer_index": 3, "explanation": "Metformin holding rules apply to iodinated contrast; ACR states metformin does not need to be stopped with gadolinium at approved doses.", "subcategory": "Patient Interactions and Management" }, { "q": "A claustrophobic outpatient is given an oral anxiolytic before a brain MRI. What must be confirmed before the medication is given?", "options": [ "An adult is available to drive the patient home after the exam", "The patient has fasted for at least 12 hours", "The patient's eGFR is above 60 mL/min/1.73 m²", "The patient has had a prior reaction to gadolinium" ], "answer_index": 0, "explanation": "Oral sedatives impair alertness and reaction time, so the patient must not drive and needs a responsible adult to take them home.", "subcategory": "Patient Interactions and Management" }, { "q": "A pregnant patient's referring physician requests a gadolinium-enhanced MRI. Which statement reflects ACR guidance?", "options": [ "Give gadolinium only if it is essential and the benefit clearly outweighs possible fetal risk", "Gadolinium does not cross the placenta, so no special approach is needed", "Gadolinium is safe at any dose in pregnancy and needs no discussion", "Gadolinium may be given only during the first trimester" ], "answer_index": 0, "explanation": "Gadolinium crosses the placenta, so ACR recommends using it in pregnancy only when it is essential and the expected benefit outweighs the potential risk.", "subcategory": "Patient Interactions and Management" }, { "q": "A technologist is stuck with a used needle while removing an IV after a contrast MRI. What should the technologist do first?", "options": [ "Finish the shift and report the injury at the end of the day", "Wash the site with soap and water, then report the exposure right away", "Squeeze the site hard and apply bleach to the wound", "Apply a bandage and report only if symptoms develop later" ], "answer_index": 1, "explanation": "After a needlestick, wash with soap and water and report immediately so post-exposure evaluation and prophylaxis can begin without delay.", "subcategory": "Patient Interactions and Management" }, { "q": "A patient weighing about 230 kg is scheduled for a lumbar spine MRI. What should the technologist check first?", "options": [ "Whether the coil can be skipped to save space in the bore", "Whether the exam can be done with the table outside the bore", "Whether the patient is within the table weight limit and fits the bore without touching its wall", "Whether the patient can be scanned prone to reduce body width" ], "answer_index": 2, "explanation": "Exceeding the table weight limit or forcing a patient into the bore risks equipment failure, injury, and RF burns from skin contact with the bore.", "subcategory": "Patient Interactions and Management" } ] }, { "id": "safety", "name": "Safety", "main_points": [ "The ACR four-zone model controls access: Zone I is public, Zone II is reception and screening, Zone III is restricted to screened people under MR personnel control, and Zone IV is the magnet room.", "Level 2 MR personnel have advanced safety training (e.g., thermal loading, burns, nerve stimulation) and may screen patients and supervise Zone III/IV access; Level 1 personnel have basic safety training.", "Screen every patient and visitor for implants, foreign bodies (especially metal in the orbits), prior surgeries, pregnancy, and external items such as medication patches, piercings, and clothing with metallic fibers.", "For any implant, identify the exact make and model, check its MR Safe, MR Conditional, or MR Unsafe labeling, and follow every condition (field strength, maximum spatial gradient, SAR or B1+rms, slew rate).", "Translational (projectile) force is greatest where the static field's spatial gradient is steepest, usually near the bore opening; rotational torque is greatest at isocenter where the field is strongest.", "RF energy deposits heat measured as specific absorption rate (SAR, W/kg); SAR rises with the square of field strength and of flip angle and with more RF pulses per unit time (e.g., FSE with short TR).", "Prevent RF burns by removing unneeded conductors, keeping cables straight and away from the bore, avoiding skin-to-skin loops (crossed ankles, clasped hands), and padding the patient away from the bore wall.", "Rapidly switching gradients (dB/dt) can cause peripheral nerve stimulation, magnetophosphenes, and loud acoustic noise; hearing protection must be provided to every patient.", "The magnetohydrodynamic effect elevates the ECG T-wave because flowing blood is a conductor moving in the static field; it does not mean ischemia.", "Under FDA guidance, static fields up to 8 T are a nonsignificant risk for adults, children, and infants over 1 month; the limit is 4 T for neonates (1 month or younger).", "A quench rapidly boils off liquid helium; if the quench vent fails, helium can displace oxygen and build pressure in the scan room, so evacuate and ventilate. Quench only in true emergencies, such as a person pinned by a ferromagnetic object.", "The 5-gauss (0.5 mT) line marks the fringe-field boundary beyond which the general public, including people with pacemakers, can safely stay." ], "vocabulary": [ { "term": "Zone IV", "definition": "The MR scanner room itself, where the static field is always present." }, { "term": "Level 2 MR personnel", "definition": "Staff with extensive MR safety training who may screen patients and control access to Zones III and IV." }, { "term": "MR Safe", "definition": "An item with no known hazards in any MR environment, labeled with a green square symbol." }, { "term": "MR Conditional", "definition": "An item shown safe only under specified MR conditions, labeled with a yellow triangle." }, { "term": "MR Unsafe", "definition": "An item that poses unacceptable risk in the MR environment, labeled with a red circle and slash." }, { "term": "Spatial field gradient", "definition": "The rate at which static field strength changes with distance, which drives translational force on ferromagnetic objects." }, { "term": "Projectile effect", "definition": "A ferromagnetic object being pulled toward the magnet at high speed by translational force." }, { "term": "Torque", "definition": "The rotational force that tries to align an elongated ferromagnetic object with the static field." }, { "term": "Specific absorption rate (SAR)", "definition": "RF power absorbed per kilogram of tissue (W/kg), used to limit patient heating." }, { "term": "B1+rms", "definition": "The time-averaged RF transmit field, increasingly used in implant conditions instead of SAR." }, { "term": "Conductive loop", "definition": "A closed path formed by cables or the patient's own body in which RF can induce current and cause a burn." }, { "term": "dB/dt", "definition": "The rate of change of the gradient magnetic field over time, which can induce currents in nerves." }, { "term": "Peripheral nerve stimulation", "definition": "Tingling or twitching caused by currents that rapidly switching gradients induce in peripheral nerves." }, { "term": "Magnetophosphenes", "definition": "Brief flashes of light the patient sees, caused by changing magnetic fields acting on the retina." }, { "term": "Magnetohydrodynamic effect", "definition": "Voltage generated by blood flowing through the static field, causing ECG T-wave elevation." }, { "term": "Quench", "definition": "Sudden loss of superconductivity in which liquid helium boils off and the magnetic field collapses." }, { "term": "5-gauss line", "definition": "The fringe-field boundary (0.5 mT) beyond which the public and pacemaker patients may safely stay." }, { "term": "Faraday cage", "definition": "The copper or aluminum RF shield around the scan room that blocks outside radiofrequency noise." } ], "quiz": [ { "q": "In the ACR four-zone model, which zone contains the MR scanner?", "options": [ "Zone I", "Zone II", "Zone IV", "Zone III" ], "answer_index": 2, "explanation": "Zone IV is the magnet room; Zone III is the restricted area (usually the control room) that leads to it." }, { "q": "A device carries a yellow triangle label reading 'MR' inside. What does this mean?", "options": [ "It is MR Conditional and can be scanned only under its specified conditions", "It is MR Safe in all MR environments", "It is MR Unsafe and must never enter Zone IV", "Its MR status has not been tested" ], "answer_index": 0, "explanation": "The yellow triangle denotes MR Conditional; the exact field strength, spatial gradient, and RF limits must be checked." }, { "q": "Where is translational force on a ferromagnetic object usually greatest?", "options": [ "At isocenter, where the field is most uniform", "At the 5-gauss line", "In the control room behind the RF shield", "Near the bore opening, where the spatial field gradient is steepest" ], "answer_index": 3, "explanation": "Translational pull depends on the spatial gradient, which peaks near the bore entrance, not at isocenter." }, { "q": "All else equal, which change increases SAR the most?", "options": [ "Lengthening the TR", "Moving the patient from a 1.5 T to a 3 T scanner", "Lowering the flip angle", "Reducing the echo train length" ], "answer_index": 1, "explanation": "SAR scales with the square of field strength, so doubling B0 roughly quadruples SAR; the other changes lower SAR." }, { "q": "A patient reports tingling in the shoulders during an echo-planar diffusion scan. What is the most likely cause?", "options": [ "RF heating from a conductive loop", "Peripheral nerve stimulation from rapidly switching gradients", "Translational force on an implant", "The magnetohydrodynamic effect" ], "answer_index": 1, "explanation": "Fast gradient switching (high dB/dt), as in EPI, can induce currents in peripheral nerves that feel like tingling." }, { "q": "During cardiac gating, the T-wave on the monitor appears falsely elevated once the patient is in the bore. This is due to:", "options": [ "Peripheral nerve stimulation", "Cryogen boil-off", "Magnetophosphenes", "The magnetohydrodynamic effect" ], "answer_index": 3, "explanation": "Blood, a conductor flowing through the static field, generates a voltage that adds to the ECG during the T-wave." }, { "q": "A patient lies with hands clasped together over the abdomen. Which risk does this create?", "options": [ "An RF burn from a conductive skin-to-skin loop", "Increased projectile risk", "Aliasing artifact only", "Magnetophosphenes" ], "answer_index": 0, "explanation": "Touching hands or thighs can form a current loop during RF transmission; insulating pads should separate skin surfaces." }, { "q": "During a quench, the vent pipe fails and helium enters the scan room. What is the main immediate hazard?", "options": [ "Ionizing radiation exposure", "Increased static field strength", "Displacement of oxygen, causing asphyxiation", "Contrast reaction" ], "answer_index": 2, "explanation": "Escaping helium displaces breathable air and is extremely cold; people should evacuate and the room must be ventilated." }, { "q": "What is the most effective routine measure against acoustic-noise injury during MRI?", "options": [ "Use only spin-echo sequences", "Increase the slew rate", "Scan only in the morning", "Provide earplugs and/or headphones to every patient" ], "answer_index": 3, "explanation": "Gradient noise can exceed safe levels, so hearing protection is required for all patients regardless of sequence." }, { "q": "A patient arrives wearing a transdermal medication patch with a metallic backing. What should be done?", "options": [ "Scan normally, since patches are always MR Safe", "Have it removed (with ordering-provider approval) before scanning to prevent a burn", "Tape a coil directly over the patch", "Cover the patch with an ice pack" ], "answer_index": 1, "explanation": "Metallic foil in some patches can heat during RF transmission; removal and later replacement follow physician direction." }, { "q": "Which person may be responsible for screening patients and controlling access to Zones III and IV?", "options": [ "Level 1 MR personnel", "Non-MR personnel", "Level 2 MR personnel", "Any visitor who completed a screening form" ], "answer_index": 2, "explanation": "Level 2 MR personnel have extensive MR safety training and oversee screening and Zone III/IV access." }, { "q": "Under FDA guidance, up to what static field strength is MRI considered a nonsignificant risk for adults?", "options": [ "8 T", "1.5 T", "3 T", "4 T" ], "answer_index": 0, "explanation": "The FDA lists 8 T as the nonsignificant-risk limit for adults, children, and infants over 1 month; 4 T applies to neonates." } ], "bank": [ { "q": "In the ACR four-zone model, where are patients typically greeted and screened under the supervision of MR personnel, between public and restricted areas?", "options": [ "Zone IV", "Zone I", "Zone III", "Zone II" ], "answer_index": 3, "explanation": "Zone II is the interface between the public Zone I and the strictly controlled Zones III and IV; screening histories are taken there.", "subcategory": "MRI Screening and Safety" }, { "q": "A housekeeper has completed basic MR safety education so they can work safely in Zone III. Under ACR terminology, this person is:", "options": [ "The MR Medical Director", "Level 1 MR personnel", "Level 2 MR personnel", "Non-MR personnel" ], "answer_index": 1, "explanation": "Level 1 personnel have passed minimal safety education for their own safety in Zone III; Level 2 personnel have extensive training in MR hazards.", "subcategory": "MRI Screening and Safety" }, { "q": "A small electrical fire starts in the MR scan room. Which extinguisher may be brought into Zone IV?", "options": [ "The extinguisher carried by responding firefighters", "Any standard steel CO2 extinguisher", "A standard dry-chemical extinguisher in a steel canister", "An MR Conditional (non-ferromagnetic) extinguisher" ], "answer_index": 3, "explanation": "Ferromagnetic extinguishers become projectiles; only MR Conditional extinguishers belong in Zone IV, and outside responders should be kept out unless the field is removed.", "subcategory": "MRI Screening and Safety" }, { "q": "A patient with an MR Conditional pacemaker system is scheduled for MRI. What must occur before scanning?", "options": [ "Nothing; MR Conditional devices can be scanned under any conditions", "The device is programmed into its MR mode by qualified personnel, and the patient is monitored during the scan within the system's labeled conditions", "Scan only on a 3 T system with SAR set to the first level controlled mode", "The pacemaker generator must be removed surgically" ], "answer_index": 1, "explanation": "MR Conditional cardiac devices require MR-mode programming, monitoring, and strict adherence to the labeled conditions, with reprogramming afterward.", "subcategory": "MRI Screening and Safety" }, { "q": "In which situation is an intentional magnet quench appropriate?", "options": [ "The building loses electrical power", "A person is pinned against the magnet by a large ferromagnetic object", "A paperclip flies into the bore and sticks to it", "A patient in the bore goes into cardiac arrest" ], "answer_index": 1, "explanation": "A quench removes the field so a pinned person can be freed (or for a fire threatening life); a cardiac arrest is handled by removing the patient from Zone IV.", "subcategory": "MRI Screening and Safety" }, { "q": "A patient who works as a welder reports he may have had metal in his eye but never had it removed. What is the appropriate next step?", "options": [ "Ask the patient to wear an eye patch during the scan", "Proceed, because intraocular metal is not a concern at 1.5 T", "Scan the head only with a low SAR", "Screen with orbital radiographs (or review prior CT) before allowing MRI" ], "answer_index": 3, "explanation": "A retained orbital metal fragment can move and injure the eye; history of metal exposure warrants imaging clearance before MRI.", "subcategory": "MRI Screening and Safety" }, { "q": "Where is rotational force (torque) on a ferromagnetic object generally greatest?", "options": [ "Where the spatial field gradient is steepest at the bore entrance", "At or near isocenter, where the static field is strongest", "At the scanner's control console", "Just outside the 5-gauss line" ], "answer_index": 1, "explanation": "Torque scales with static field strength and peaks at isocenter, while translational attraction peaks where the spatial gradient is steepest.", "subcategory": "MRI Screening and Safety" }, { "q": "The 5-gauss line marks the boundary beyond which the static field is considered safe for the general public. 5 gauss equals:", "options": [ "0.05 T", "5 mT", "0.5 mT", "50 mT" ], "answer_index": 2, "explanation": "1 tesla = 10,000 gauss, so 5 gauss = 0.0005 T = 0.5 mT.", "subcategory": "MRI Screening and Safety" }, { "q": "Which ASTM label identifies an item as MR Unsafe?", "options": [ "A blue circle with a white 'MR' inside", "A green square with 'MR' inside", "A yellow triangle with 'MR' inside", "A red circle with a diagonal line through the letters 'MR'" ], "answer_index": 3, "explanation": "Under ASTM F2503 the MR Unsafe icon is red with a diagonal bar; MR Conditional is a yellow triangle and MR Safe is green.", "subcategory": "MRI Screening and Safety" }, { "q": "How should ECG leads be arranged for a gated cardiac MRI to reduce the risk of RF burns?", "options": [ "Run the leads straight without loops or crossings, keep them away from the bore wall, and pad between leads and skin", "Coil excess lead length into a loop on the patient's chest", "Tape the leads to the inside of the bore", "Use standard non-MR electrodes with metal snaps" ], "answer_index": 0, "explanation": "Loops and contact with the bore concentrate induced currents; straight, padded MR Conditional leads reduce heating.", "subcategory": "MRI Screening and Safety" }, { "q": "A technologist is 5 months pregnant. According to ACR guidance, which restriction applies?", "options": [ "She may only work at 1.5 T or below", "She may work in Zones III and IV but should not remain in Zone IV while the scanner is acquiring data", "She must wear a lead apron in Zone IV", "She must stop working in MRI for the rest of the pregnancy" ], "answer_index": 1, "explanation": "ACR permits pregnant staff to work in the MR environment but advises against remaining in Zone IV during active scanning.", "subcategory": "MRI Screening and Safety" }, { "q": "A patient has a large, recently applied tattoo on the thigh within the area to be scanned. What is the appropriate approach?", "options": [ "Proceed, telling the patient to report any warmth; a cold compress over the tattoo is an option", "Cover the tattoo with an aluminum foil shield", "Scan only with gradient-echo sequences", "Cancel the exam; tattoos are an absolute contraindication" ], "answer_index": 0, "explanation": "Tattoos rarely cause problems; informing the patient and using a cold compress addresses the small risk of heating or irritation.", "subcategory": "MRI Screening and Safety" }, { "q": "A patient arrives wearing an insulin pump and a continuous glucose monitor. What should be done?", "options": [ "Turn the pump off but leave it attached during the scan", "Leave them on but cover them with a towel", "Remove them per manufacturer instructions before the patient enters Zone IV, with a plan for glucose management", "Leave them on, because they are designed for MRI" ], "answer_index": 2, "explanation": "Most insulin pumps and CGMs are labeled MR Unsafe and can be damaged or malfunction, so they are removed before entering Zone IV.", "subcategory": "MRI Screening and Safety" }, { "q": "Under IEC 60601-2-33, what is the whole-body averaged SAR limit in Normal Operating Mode?", "options": [ "4 W/kg", "2 W/kg", "8 W/kg", "1 W/kg" ], "answer_index": 1, "explanation": "Normal Operating Mode limits whole-body SAR to 2 W/kg averaged over 6 minutes; First Level Controlled Mode allows 4 W/kg.", "subcategory": "MRI Screening and Safety" }, { "q": "An MR Conditional implant label lists a maximum spatial field gradient of 3,000 gauss/cm. This condition mainly limits which hazard?", "options": [ "Peripheral nerve stimulation from the gradients", "Acoustic noise near the device", "RF heating of the device's tissues", "Translational (attractive) force on the device" ], "answer_index": 3, "explanation": "The spatial field gradient value limits translational attraction, which is greatest where the static field changes most quickly near the bore opening.", "subcategory": "MRI Screening and Safety" }, { "q": "A patient's implant is labeled MR Conditional only at 1.5 T. The only open slot is on a 3 T scanner. What is correct?", "options": [ "Scan at 3 T, provided the patient is closely monitored", "Scan only on a 1.5 T system that meets all of the device's labeled conditions", "Scan at 3 T, since conditional devices are safe at any field strength", "Scan at 3 T, using low-SAR sequences to compensate" ], "answer_index": 1, "explanation": "MR Conditional labeling applies only under the stated conditions; a device tested only at 1.5 T has not been shown to be safe at 3 T.", "subcategory": "MRI Screening and Safety" }, { "q": "A patient reports having a spinal cord stimulator but does not know its make or model. What is the most appropriate step?", "options": [ "Find out the exact device and its labeling (implant card or records) before scanning", "Scan at 1.5 T, since most stimulators are MR Conditional", "Cancel MRI permanently, since all stimulators are MR Unsafe", "Scan with a body coil, since a local coil would heat the leads" ], "answer_index": 0, "explanation": "MR conditions depend on the specific device and lead combination, so it must be identified and its labeling reviewed before scanning.", "subcategory": "MRI Screening and Safety" }, { "q": "A brain MRI uses a transmit/receive head coil. What is the maximum SAR allowed when averaged over the head?", "options": [ "3.2 W/kg", "10 W/kg", "2 W/kg", "4 W/kg" ], "answer_index": 0, "explanation": "The IEC limit for head-averaged SAR is 3.2 W/kg; whole-body SAR is limited to 2 W/kg in Normal Mode and 4 W/kg in First Level Controlled Mode.", "subcategory": "MRI Screening and Safety" }, { "q": "At an MRI facility, who holds overall responsibility for MR safety policies and for decisions on scanning patients with uncertain implants?", "options": [ "The referring physician of each patient", "The Level 1 MR personnel on duty", "The equipment vendor's service engineer", "The MR Medical Director (MRMD)" ], "answer_index": 3, "explanation": "Under ACR guidance, the MR Medical Director oversees MR safety policies and is ultimately responsible for safety decisions at the site, supported by the MR safety officer.", "subcategory": "MRI Screening and Safety" }, { "q": "In Normal Operating Mode, IEC 60601-2-33 limits a patient's core body temperature rise to:", "options": [ "1°C", "2°C", "0.5°C", "0.1°C" ], "answer_index": 2, "explanation": "Normal Mode limits core temperature rise to 0.5°C; First Level Controlled Mode allows up to 1°C.", "subcategory": "MRI Screening and Safety" }, { "q": "An unconscious trauma patient from the ED needs an urgent brain MRI and cannot answer screening questions. What is the best approach?", "options": [ "Wait until the patient wakes up, however long that takes", "Scan right away, since an urgent exam overrides screening", "Get the history from family and records, and use radiographs or prior CT to look for metal", "Use only a handheld metal detector, then scan" ], "answer_index": 2, "explanation": "When a patient cannot be screened directly, MR personnel use family, records, and imaging to find implants and foreign bodies before entering Zone IV.", "subcategory": "MRI Screening and Safety" }, { "q": "During positioning, a large patient's arm rests directly against the inner wall of the bore. What should be done?", "options": [ "Place insulating pads between the skin and the bore wall", "Proceed, since the bore wall contains no RF energy", "Wrap the arm in an aluminum blanket to reflect RF energy", "Cover the arm with a damp towel to absorb any heat" ], "answer_index": 0, "explanation": "Skin touching the bore can lead to RF burns, so nonconductive padding should keep the patient separated from the bore wall.", "subcategory": "MRI Screening and Safety" }, { "q": "A patient had an intracranial aneurysm clip placed decades ago, and the clip type cannot be identified. What is appropriate?", "options": [ "Scan, but only with the head outside the bore", "Scan, because all aneurysm clips are titanium", "Do not scan until the clip type is identified or the radiologist decides", "Scan at a lower field strength without checking further" ], "answer_index": 2, "explanation": "Some older aneurysm clips are ferromagnetic and can move or twist, with fatal results, so an unidentified clip must be resolved before scanning.", "subcategory": "MRI Screening and Safety" }, { "q": "During an unplanned quench, a white cloud of vapor fills the scan room. What should the technologist do?", "options": [ "Close the scan room door to keep the gas contained", "Turn off the console, which stops the quench immediately", "Stay in the room and finish the sequence before leaving", "Get the patient and everyone out at once, and leave the door open to vent the room" ], "answer_index": 3, "explanation": "Helium venting into the room displaces oxygen and can raise room pressure, so everyone is evacuated at once and the room is ventilated.", "subcategory": "MRI Screening and Safety" }, { "q": "A building-wide power outage shuts down the MR console and lights. What is true about the superconducting magnet?", "options": [ "The field drops to half strength until power returns", "Its static magnetic field is still present at full strength", "The field shuts down safely after about one minute", "The field drops to zero as soon as power is lost" ], "answer_index": 1, "explanation": "A superconducting magnet stays at field without external power, so Zone IV restrictions remain in force during an outage.", "subcategory": "MRI Screening and Safety" }, { "q": "What is the main purpose of active shielding on a superconducting magnet?", "options": [ "To reduce acoustic noise from gradient switching", "To shrink the fringe field so the 5-gauss line stays closer to the magnet", "To increase the strength of the main field at isocenter", "To block outside RF interference from entering the scan room" ], "answer_index": 1, "explanation": "Active shielding uses extra superconducting coils to cancel much of the fringe field, which keeps the 5-gauss line closer to the magnet.", "subcategory": "MRI Screening and Safety" }, { "q": "Firefighters respond to an alarm in the MRI suite carrying air tanks and axes. What should MR personnel do?", "options": [ "Meet them and keep them out of Zone IV unless the magnet is quenched or they are cleared", "Lead them into the scan room as quickly as possible", "Let them in, since emergency staff are exempt from screening", "Allow them in if they remove only their helmets" ], "answer_index": 0, "explanation": "Emergency responders' equipment is often ferromagnetic, so MR personnel must control access to Zone IV and tell them the field is always on.", "subcategory": "MRI Screening and Safety" }, { "q": "A site installs a ferromagnetic detection system at the Zone IV entrance. According to ACR guidance, how should it be used?", "options": [ "As an addition to careful screening, never as a replacement for it", "Only for staff, not for patients", "As the only step needed for patients with implants", "As a replacement for written screening forms" ], "answer_index": 0, "explanation": "Ferromagnetic detectors help find missed objects but cannot detect non-ferromagnetic implants or assess device conditions, so full screening is still needed.", "subcategory": "MRI Screening and Safety" }, { "q": "A patient arrives in athletic leggings labeled as having silver antimicrobial fibers. What should be done?", "options": [ "Turn the leggings inside out so the fibers face away", "Allow them, since silver is not attracted to the magnet", "Allow them, but put a towel between the leggings and the coil", "Have the patient change into a facility gown, since metallic fibers can heat" ], "answer_index": 3, "explanation": "Clothing with metallic threads can heat and cause burns even when not ferromagnetic, so changing into a facility gown is recommended.", "subcategory": "MRI Screening and Safety" }, { "q": "A neurostimulator's MR Conditional label limits B1+rms to 2.0 µT. What does B1+rms describe?", "options": [ "The rate of change of the gradient fields", "The strength of the static magnetic field at isocenter", "The steepness of the fringe field near the bore", "The time-averaged RF transmit field the patient is exposed to" ], "answer_index": 3, "explanation": "B1+rms is the root-mean-square RF transmit field; it is a more scanner-independent measure of RF exposure than estimated SAR and is used in many device labels.", "subcategory": "MRI Screening and Safety" }, { "q": "A patient has a bullet fragment in the soft tissue of the thigh from an old gunshot wound. What determines whether MRI may proceed?", "options": [ "Nothing; retained bullets are always safe to scan", "Whether the fragment is outside the area being scanned", "A radiologist's risk-benefit review of the fragment's location and likely composition", "The patient's statement that the area does not hurt" ], "answer_index": 2, "explanation": "Bullets may be ferromagnetic; the risk depends on location near vital structures and composition, so the radiologist decides after imaging review.", "subcategory": "MRI Screening and Safety" }, { "q": "A patient had a coronary artery stent placed yesterday and needs an MRI. What is generally true?", "options": [ "Most current coronary stents are MR Conditional and may be scanned under their labeled conditions", "Stents may be scanned only if the chest is outside the bore", "Coronary stents are MR Unsafe and rule out MRI permanently", "All stents need a 6-week wait for tissue ingrowth first" ], "answer_index": 0, "explanation": "Most modern coronary stents are labeled MR Conditional, often with no waiting period, but the specific device's labeled conditions must be followed.", "subcategory": "MRI Screening and Safety" }, { "q": "A parent wants to stay in the scan room to comfort a child during an MRI. What is required?", "options": [ "The parent must stay behind the 5-gauss line inside Zone IV", "Nothing, because only the patient enters the bore", "The parent must complete the same MR safety screening as a patient before entering Zone IV", "The parent needs to empty their pockets only" ], "answer_index": 2, "explanation": "Anyone entering Zone IV, including family members, must be screened for implants and metallic objects and given hearing protection.", "subcategory": "MRI Screening and Safety" }, { "q": "A fast spin-echo sequence is blocked because it exceeds the SAR limit. Which change most directly lowers SAR?", "options": [ "Increase the number of slices", "Lower the refocusing flip angle", "Increase the echo train length", "Shorten the TR" ], "answer_index": 1, "explanation": "SAR rises with the square of the flip angle and with RF pulses per unit time, so lower refocusing angles (or longer TR, fewer slices) reduce SAR.", "subcategory": "MRI Screening and Safety" }, { "q": "An inpatient arrives on a stretcher with a standard steel oxygen cylinder attached. What should happen before the patient enters Zone IV?", "options": [ "Tape the cylinder firmly to the stretcher frame", "Switch to wall oxygen or an MR Conditional cylinder, and remove the steel tank", "Take the tank in but keep it at the foot of the table", "Shut the tank off, since an empty tank is not attracted" ], "answer_index": 1, "explanation": "Steel oxygen cylinders are ferromagnetic projectiles; they must stay outside Zone IV and be replaced with wall oxygen or MR Conditional equipment.", "subcategory": "MRI Screening and Safety" } ] }, { "id": "image-production", "name": "Image Production", "main_points": [ "Larmor equation: ω0 = γ × B0. For hydrogen, γ ≈ 42.58 MHz/T, so precession is about 63.9 MHz at 1.5 T and about 127.7 MHz at 3 T.", "A 90° RF pulse at the Larmor frequency tips net magnetization into the transverse plane and creates phase coherence; the precessing magnetization induces signal (FID) in the receiver coil by Faraday's law.", "T1 is the time for longitudinal magnetization to recover to 63% of its maximum; T2 is the time for transverse magnetization to decay to 37%. Fat has short T1 (bright on T1W), and fluid has long T2 (bright on T2W). T2* also includes field-inhomogeneity dephasing.", "Weighting: T1W uses short TR and short TE; T2W uses long TR and long TE; PD uses long TR and short TE. In GRE, a larger flip angle adds T1 weighting.", "Scan time for 2D SE = TR × phase-encoding steps × NEX; FSE divides by echo train length, and 3D multiplies by the number of partitions. Parallel imaging divides time by the acceleration factor at an SNR cost.", "SNR rises with voxel volume and with the square root of NEX; narrowing receiver bandwidth raises SNR but worsens chemical shift and lengthens minimum TE. Doubling NEX doubles time for only a ~41% SNR gain.", "Spatial localization: the slice-select gradient is on during RF, the phase-encoding gradient steps between TRs, and the frequency (readout) gradient is on during the echo. The center of k-space holds contrast and SNR; the periphery holds edges and detail.", "Know the classic artifacts and fixes: aliasing (enlarge FOV or use phase oversampling); chemical shift in the frequency direction (widen bandwidth); motion ghosting in the phase direction (gating, saturation bands, swap phase/frequency); and susceptibility (use FSE, wider bandwidth, shorter TE).", "Fat suppression options: spectral fat saturation (needs a homogeneous field); STIR, with a TI of about 140–160 ms at 1.5 T (not after gadolinium); and Dixon in-phase/out-of-phase water–fat separation. FLAIR uses a long TI (~2,000–2,500 ms) to null CSF.", "Diffusion-weighted imaging (usually EPI) uses b-values to sensitize the image to water motion; restricted diffusion is bright on DWI and dark on the ADC map.", "MRA techniques: time-of-flight relies on inflow of unsaturated blood (slices perpendicular to flow, sat band to null the opposite flow); phase contrast uses bipolar gradients and a VENC set just above the expected peak velocity; contrast-enhanced MRA relies on gadolinium T1 shortening.", "Images are converted from k-space by Fourier transform, sampled per the Nyquist theorem (at least twice the highest frequency), stored and sent in DICOM format to PACS, and checked with QC tests (center frequency, transmit gain, SNR, geometric accuracy, slice thickness)." ], "vocabulary": [ { "term": "Larmor frequency", "definition": "The precessional frequency of a nucleus, equal to the gyromagnetic ratio times field strength." }, { "term": "Gyromagnetic ratio", "definition": "A constant for each nucleus (42.58 MHz/T for hydrogen) relating precession frequency to field strength." }, { "term": "Net magnetization vector", "definition": "The sum of all proton magnetic moments, aligned with B0 at equilibrium." }, { "term": "Free induction decay (FID)", "definition": "The decaying signal induced in the receiver coil right after an RF excitation pulse." }, { "term": "T1 recovery", "definition": "Spin-lattice relaxation; regrowth of longitudinal magnetization after excitation." }, { "term": "T2 decay", "definition": "Spin-spin relaxation; loss of transverse magnetization from proton interactions." }, { "term": "T2*", "definition": "Transverse decay that combines true T2 with dephasing from magnetic field inhomogeneity." }, { "term": "K-space", "definition": "The raw-data matrix of spatial frequencies that is Fourier transformed into the image." }, { "term": "Fast Fourier transform (FFT)", "definition": "The mathematical process that converts k-space frequency data into an image." }, { "term": "Receiver bandwidth", "definition": "The range of frequencies sampled during readout; narrower bandwidth means more SNR and more chemical shift." }, { "term": "NEX / NSA", "definition": "Number of excitations or signal averages; SNR rises with its square root, and scan time rises in proportion." }, { "term": "Echo train length (ETL)", "definition": "The number of echoes collected per TR in fast spin echo, each filling a different k-space line." }, { "term": "Effective TE", "definition": "In FSE, the echo time of the echo placed in the center of k-space, which sets image contrast." }, { "term": "Inversion time (TI)", "definition": "Time between the 180° inversion pulse and the 90° excitation, chosen to null a tissue." }, { "term": "Chemical shift artifact", "definition": "A bright/dark band at fat–water interfaces along the frequency direction from their ~3.5 ppm frequency difference." }, { "term": "Aliasing", "definition": "Wrap-around of anatomy outside the FOV into the image, usually in the phase direction." }, { "term": "Gibbs (truncation) artifact", "definition": "Parallel lines near sharp high-contrast edges from undersampling; reduced by increasing the matrix." }, { "term": "VENC", "definition": "Velocity encoding; the maximum velocity a phase-contrast sequence encodes without aliasing." }, { "term": "b-value", "definition": "The strength and timing of diffusion gradients, in s/mm², that sets diffusion weighting." }, { "term": "Nyquist theorem", "definition": "A signal must be sampled at least twice per cycle of its highest frequency to be represented accurately." } ], "quiz": [ { "q": "What is the approximate precessional frequency of hydrogen protons in a 3 T magnet?", "options": [ "42.6 MHz", "63.9 MHz", "127.7 MHz", "255.4 MHz" ], "answer_index": 2, "explanation": "Larmor frequency = 42.58 MHz/T × 3 T ≈ 127.7 MHz; 63.9 MHz is the value at 1.5 T." }, { "q": "Which spin-echo parameter pair produces a T1-weighted image?", "options": [ "TR 500 ms / TE 15 ms", "TR 3,500 ms / TE 100 ms", "TR 3,000 ms / TE 20 ms", "TR 2,500 ms / TE 120 ms" ], "answer_index": 0, "explanation": "Short TR and short TE emphasize T1 differences; long TR/short TE gives PD, and long TR/long TE gives T2 weighting." }, { "q": "If NEX is increased from 1 to 2 with all other factors unchanged, what happens?", "options": [ "SNR doubles and scan time doubles", "SNR increases by about 41% and scan time is unchanged", "SNR doubles and scan time is halved", "SNR increases by about 41% and scan time doubles" ], "answer_index": 3, "explanation": "SNR is proportional to the square root of NEX (√2 ≈ 1.41), while time increases in direct proportion." }, { "q": "An FSE sequence uses TR 3,000 ms, 256 phase-encoding steps, NEX 2, and ETL 16. What is the scan time?", "options": [ "25 min 36 s", "1 min 36 s", "3 min 12 s", "48 s" ], "answer_index": 1, "explanation": "Time = TR × phase steps × NEX ÷ ETL = 3 s × 256 × 2 ÷ 16 = 96 s." }, { "q": "Which change reduces chemical shift artifact?", "options": [ "Moving to a higher field strength", "Increasing the receiver bandwidth", "Decreasing the receiver bandwidth", "Increasing NEX" ], "answer_index": 1, "explanation": "A wider bandwidth spreads more frequency per pixel, so the fat–water shift covers fewer pixels; higher B0 makes it worse." }, { "q": "On a coronal abdomen image, the patient's arms wrap into the opposite side of the image. Which change corrects this?", "options": [ "Decrease the FOV", "Increase the slice thickness", "Shorten the TE", "Increase the FOV or apply phase oversampling (no phase wrap)" ], "answer_index": 3, "explanation": "Aliasing occurs when anatomy outside the FOV is excited; covering it with a larger FOV or oversampling removes the wrap." }, { "q": "At 1.5 T, which inversion time is used for STIR fat suppression?", "options": [ "About 150 ms", "About 20 ms", "About 600 ms", "About 2,200 ms" ], "answer_index": 0, "explanation": "A TI near 0.69 × fat's T1 (≈140–160 ms at 1.5 T) nulls fat; around 2,200 ms nulls CSF in FLAIR." }, { "q": "What information is stored mainly in the center of k-space?", "options": [ "Fine edge detail only", "Patient demographic data", "Image contrast and signal", "Gradient calibration values" ], "answer_index": 2, "explanation": "Low spatial frequencies at the center determine contrast and SNR; high frequencies at the periphery define edges and detail." }, { "q": "How does an acute infarct with restricted diffusion appear?", "options": [ "Dark on DWI and bright on the ADC map", "Bright on both DWI and the ADC map", "Dark on both DWI and the ADC map", "Bright on DWI and dark on the ADC map" ], "answer_index": 3, "explanation": "Restricted water motion keeps signal high on high-b DWI and gives a low apparent diffusion coefficient." }, { "q": "For 2D time-of-flight MRA of the carotid arteries, where should the saturation band go to suppress jugular venous signal?", "options": [ "Inferior to the imaging slices", "Superior to the imaging slices", "Anterior to the trachea", "Directly over the carotid bifurcation" ], "answer_index": 1, "explanation": "Jugular blood flows downward from the head, so a superior sat band saturates it before it enters the slices while arterial inflow from below stays bright." }, { "q": "Which change best reduces susceptibility artifact around orthopedic hardware?", "options": [ "Use gradient echo with a longer TE", "Narrow the receiver bandwidth", "Use fast spin echo instead of gradient echo, with a wider receiver bandwidth", "Increase field strength to 3 T" ], "answer_index": 2, "explanation": "180° refocusing pulses in FSE cancel static dephasing, and wider bandwidth reduces distortion; GRE, long TE, and higher B0 worsen it." }, { "q": "Parallel imaging with an acceleration factor of 2 is applied. What is the expected result?", "options": [ "Scan time is roughly halved and SNR decreases", "Scan time doubles and SNR increases", "Scan time is unchanged and SNR doubles", "Spatial resolution is halved with no SNR change" ], "answer_index": 0, "explanation": "Parallel imaging skips phase-encoding lines using coil sensitivity data, cutting time by about R at an SNR cost of at least √R." } ], "bank": [ { "q": "What is the gyromagnetic ratio of the hydrogen proton?", "options": [ "42.58 MHz/T", "127.7 MHz/T", "21.29 MHz/T", "63.86 MHz/T" ], "answer_index": 0, "explanation": "Hydrogen precesses at 42.58 MHz per tesla, giving about 63.9 MHz at 1.5 T.", "subcategory": "Physical Principles of Image Formation" }, { "q": "T1 relaxation time is the time it takes for longitudinal magnetization to recover to what fraction of its maximum?", "options": [ "90%", "37%", "63%", "50%" ], "answer_index": 2, "explanation": "T1 is the time for longitudinal magnetization to regrow to about 63% of its full value.", "subcategory": "Physical Principles of Image Formation" }, { "q": "T2 relaxation time is the time it takes for transverse magnetization to decay to what fraction of its initial value?", "options": [ "50%", "10%", "63%", "37%" ], "answer_index": 3, "explanation": "T2 is the time for transverse magnetization to decay to about 37% (lose 63%) of its initial value.", "subcategory": "Physical Principles of Image Formation" }, { "q": "Why is T2* always shorter than T2 for the same tissue?", "options": [ "T2* ignores spin-spin interactions", "T2* is measured only at higher field strengths", "T2* also includes dephasing from magnetic field inhomogeneities and susceptibility effects", "T2* depends on the TR rather than tissue properties" ], "answer_index": 2, "explanation": "T2* decay combines true spin-spin relaxation with extra dephasing from field inhomogeneity.", "subcategory": "Physical Principles of Image Formation" }, { "q": "What does a 90-degree RF excitation pulse do to the net magnetization vector?", "options": [ "Aligns it more strongly with B0", "Inverts it to point opposite B0", "Removes it entirely", "Tips it from the longitudinal axis into the transverse plane" ], "answer_index": 3, "explanation": "A 90-degree pulse rotates the net magnetization into the transverse plane, where it induces signal in the receiver coil.", "subcategory": "Physical Principles of Image Formation" }, { "q": "In a spin-echo sequence, what is the purpose of the 180-degree refocusing pulse?", "options": [ "To rephase spins that dephased because of static field inhomogeneities", "To spoil residual transverse magnetization", "To invert longitudinal magnetization for fat nulling", "To select the slice location" ], "answer_index": 0, "explanation": "The 180-degree pulse reverses static dephasing so the echo reflects true T2 decay rather than T2*.", "subcategory": "Physical Principles of Image Formation" }, { "q": "Why are gradient-echo images more sensitive to susceptibility effects than spin-echo images?", "options": [ "Gradient echoes are rephased by gradient reversal, which does not correct dephasing from field inhomogeneities", "Gradient echoes are acquired only in 3D", "Gradient echoes use longer TRs", "Gradient echoes use a 180-degree refocusing pulse" ], "answer_index": 0, "explanation": "Without a 180-degree pulse, GRE signal decays with T2*, so susceptibility differences cause signal loss.", "subcategory": "Physical Principles of Image Formation" }, { "q": "Why does fat appear bright on T1-weighted images?", "options": [ "Fat has a very short T2", "Fat has a high proton density but no T1", "Fat has a short T1 relaxation time, so its longitudinal magnetization recovers quickly", "Fat has a long T1 relaxation time" ], "answer_index": 2, "explanation": "Tissues with short T1 recover more magnetization between excitations and give more signal on T1W images.", "subcategory": "Physical Principles of Image Formation" }, { "q": "Why does cerebrospinal fluid appear bright on T2-weighted images?", "options": [ "CSF has a short T1", "CSF has a short T2", "CSF has a very low proton density", "CSF has a long T2, so it keeps transverse magnetization at long TE" ], "answer_index": 3, "explanation": "Free water has a long T2, so it retains signal when a long TE is used.", "subcategory": "Physical Principles of Image Formation" }, { "q": "At 3 T, approximately what is the frequency difference between fat and water protons?", "options": [ "About 220 Hz", "About 880 Hz", "About 3.5 Hz", "About 440 Hz" ], "answer_index": 3, "explanation": "Fat and water differ by about 3.5 ppm; at 127.7 MHz that is roughly 440 Hz (about 220 Hz at 1.5 T).", "subcategory": "Physical Principles of Image Formation" }, { "q": "When is the slice-select gradient applied?", "options": [ "During the RF excitation (and refocusing) pulses", "Only during signal readout", "Between the RF pulse and the readout only", "After the echo is collected" ], "answer_index": 0, "explanation": "Turning on the slice-select gradient during the RF pulse makes only protons in the chosen slice resonate.", "subcategory": "Physical Principles of Image Formation" }, { "q": "When is the frequency-encoding (readout) gradient applied?", "options": [ "Only before the 90-degree pulse", "During the RF excitation pulse", "Between TR periods to spoil signal", "While the echo is being sampled" ], "answer_index": 3, "explanation": "The readout gradient is on during signal sampling so each position along that axis has a distinct frequency.", "subcategory": "Physical Principles of Image Formation" }, { "q": "With the transmit RF bandwidth unchanged, how can a thinner slice be achieved?", "options": [ "Increase the receiver bandwidth", "Decrease the slice-select gradient amplitude", "Increase the slice-select gradient amplitude", "Increase the NEX" ], "answer_index": 2, "explanation": "A steeper slice-select gradient means the same RF bandwidth covers a narrower range of positions.", "subcategory": "Physical Principles of Image Formation" }, { "q": "How do tissue T1 relaxation times change when moving from 1.5 T to 3 T?", "options": [ "They shorten", "They lengthen", "They become equal to T2", "They stay the same" ], "answer_index": 1, "explanation": "T1 times increase at higher field strength, which is why TR and TI values are often adjusted at 3 T.", "subcategory": "Physical Principles of Image Formation" }, { "q": "All else equal, how does SNR change when moving from 1.5 T to 3 T?", "options": [ "It stays the same", "It roughly doubles", "It increases about tenfold", "It is roughly halved" ], "answer_index": 1, "explanation": "SNR rises approximately in proportion to field strength, so doubling B0 roughly doubles SNR.", "subcategory": "Physical Principles of Image Formation" }, { "q": "If slice thickness is reduced from 6 mm to 3 mm with all else unchanged, what happens to SNR?", "options": [ "It doubles", "It is reduced to one quarter", "It is reduced by about half", "It is unchanged" ], "answer_index": 2, "explanation": "SNR is proportional to voxel volume, so halving slice thickness halves SNR.", "subcategory": "Physical Principles of Image Formation" }, { "q": "Which combination produces a proton density-weighted spin-echo image?", "options": [ "Long TR and short TE", "Short TR and short TE", "Short TR and long TE", "Long TR and long TE" ], "answer_index": 0, "explanation": "A long TR minimizes T1 effects and a short TE minimizes T2 effects, leaving proton density as the main contrast.", "subcategory": "Physical Principles of Image Formation" }, { "q": "What begins an inversion-recovery sequence?", "options": [ "A fat saturation pulse at 220 Hz", "A 90-degree excitation pulse", "A 180-degree inversion pulse", "A gradient reversal" ], "answer_index": 2, "explanation": "The 180-degree pulse inverts longitudinal magnetization; tissues then recover during the inversion time before excitation.", "subcategory": "Physical Principles of Image Formation" }, { "q": "Approximately what inversion time nulls a tissue with a given T1?", "options": [ "2.0 x T1", "0.69 x T1", "1.0 x T1", "0.37 x T1" ], "answer_index": 1, "explanation": "A tissue's magnetization crosses zero at TI = T1 x ln 2, or about 0.69 x T1.", "subcategory": "Physical Principles of Image Formation" }, { "q": "Which magnetic property describes gadolinium-based contrast agents?", "options": [ "Nonmagnetic", "Ferromagnetic", "Diamagnetic", "Paramagnetic" ], "answer_index": 3, "explanation": "Gadolinium's unpaired electrons make it paramagnetic, which shortens the T1 (and T2) of nearby protons.", "subcategory": "Physical Principles of Image Formation" }, { "q": "T2 relaxation is also known as:", "options": [ "Spin-spin relaxation", "Spin-lattice relaxation", "Chemical shift relaxation", "Longitudinal relaxation" ], "answer_index": 0, "explanation": "T2 results from energy exchange between neighboring spins, causing loss of phase coherence.", "subcategory": "Physical Principles of Image Formation" }, { "q": "What is a free induction decay (FID)?", "options": [ "Signal from the RF transmitter leaking into the room", "Noise from the gradient amplifiers", "The echo formed by a 180-degree pulse", "The signal produced right after an RF pulse, decaying with T2*" ], "answer_index": 3, "explanation": "The FID is the raw signal that appears immediately after excitation and decays rapidly from T2* effects.", "subcategory": "Physical Principles of Image Formation" }, { "q": "Why must the RF excitation pulse be applied at the Larmor frequency?", "options": [ "Only at the precessional frequency can energy be transferred to the protons (resonance)", "To keep SAR below the normal mode limit", "To avoid peripheral nerve stimulation", "To set the slice thickness" ], "answer_index": 0, "explanation": "Resonance requires matching the RF frequency to the protons' precessional frequency.", "subcategory": "Physical Principles of Image Formation" }, { "q": "On gradient-echo brain images, signal loss is seen near the sinuses and skull base. What causes this?", "options": [ "Aliasing from tissue outside the FOV", "Chemical shift of the second kind", "Truncation of high spatial frequencies", "Magnetic susceptibility differences at air-tissue interfaces" ], "answer_index": 3, "explanation": "Air and tissue magnetize differently, distorting the local field and causing rapid dephasing on GRE images.", "subcategory": "Physical Principles of Image Formation" }, { "q": "On a 2D gradient-echo sequence, blood in a vessel appears bright on the first slice it enters. Why?", "options": [ "The readout gradient amplifies flowing spins", "Blood has a very short T2", "Blood contains paramagnetic oxyhemoglobin", "Fresh, unsaturated spins flow into the slice (flow-related enhancement)" ], "answer_index": 3, "explanation": "Inflowing spins have not been saturated by prior RF pulses, so they give strong signal (the entry-slice phenomenon).", "subcategory": "Physical Principles of Image Formation" }, { "q": "Why does fast-flowing arterial blood often appear dark on spin-echo images?", "options": [ "Spin-echo uses gradient reversal for rephasing", "Arterial blood has a short T1", "Gadolinium in the blood pool suppresses signal", "Spins excited by the 90-degree pulse leave the slice before the 180-degree pulse refocuses them" ], "answer_index": 3, "explanation": "This high-velocity signal loss (flow void) happens because flowing spins don't experience both RF pulses.", "subcategory": "Physical Principles of Image Formation" }, { "q": "In a spin-echo sequence, TR is increased from 500 ms to 2,000 ms with all else unchanged. What is the main effect?", "options": [ "SNR decreases and T1 weighting increases", "SNR increases, T1 weighting decreases, and scan time increases", "Nothing changes except the number of slices decreases", "Scan time decreases and T2 weighting decreases" ], "answer_index": 1, "explanation": "A longer TR allows fuller longitudinal recovery, increasing SNR and reducing T1 contrast while lengthening the scan.", "subcategory": "Sequence Parameters and Options" }, { "q": "TE is increased from 20 ms to 100 ms. What is the main effect?", "options": [ "T1 weighting increases", "Scan time is halved", "SNR increases and T2 weighting decreases", "T2 weighting increases and SNR decreases" ], "answer_index": 3, "explanation": "A longer TE allows more transverse decay, increasing T2 contrast at the cost of signal.", "subcategory": "Sequence Parameters and Options" }, { "q": "Which gradient-echo settings produce T1 weighting?", "options": [ "Long TR, long TE, and a small flip angle", "Long TR, short TE, and a small flip angle", "Short TR, short TE, and a large flip angle", "Short TR, long TE, and a small flip angle" ], "answer_index": 2, "explanation": "A large flip angle with short TR saturates long-T1 tissues, and a short TE minimizes T2* effects.", "subcategory": "Sequence Parameters and Options" }, { "q": "Which gradient-echo settings produce T2* weighting?", "options": [ "Small flip angle, relatively long TR, and long TE", "Large flip angle, long TR, and short TE", "Small flip angle, short TR, and short TE", "Large flip angle, short TR, and short TE" ], "answer_index": 0, "explanation": "A small flip angle reduces T1 effects, and a long TE allows T2* differences to show.", "subcategory": "Sequence Parameters and Options" }, { "q": "Echo train length in an FSE sequence is increased from 8 to 24. What is the expected effect?", "options": [ "Chemical shift artifact disappears", "T1 weighting increases", "Scan time decreases, but blurring may increase and fewer slices may fit per TR", "Scan time increases and SNR increases" ], "answer_index": 2, "explanation": "Longer echo trains fill more k-space lines per TR, saving time, but later echoes have decayed signal, which can blur the image.", "subcategory": "Sequence Parameters and Options" }, { "q": "In a fast spin-echo sequence, what determines the effective TE?", "options": [ "The TE of the echoes placed in the center of k-space", "The average TE of all echoes in the train", "The first echo in the train", "The last echo in the train" ], "answer_index": 0, "explanation": "Image contrast is dominated by the center of k-space, so the echo time placed there sets the effective TE.", "subcategory": "Sequence Parameters and Options" }, { "q": "Receiver bandwidth is doubled with all else unchanged. What happens to SNR?", "options": [ "It decreases by 50%", "It doubles", "It is unchanged", "It decreases by about 29%" ], "answer_index": 3, "explanation": "SNR is inversely proportional to the square root of bandwidth, so doubling bandwidth multiplies SNR by about 0.71.", "subcategory": "Sequence Parameters and Options" }, { "q": "A square FOV is reduced from 24 cm to 12 cm with the same matrix. What happens to SNR?", "options": [ "It drops to about one half", "It doubles", "It drops to about one quarter", "It is unchanged" ], "answer_index": 2, "explanation": "Halving the FOV in both directions makes each voxel one quarter of the area, so SNR falls to about 25%.", "subcategory": "Sequence Parameters and Options" }, { "q": "The phase matrix is increased from 192 to 384 with all else unchanged. What results?", "options": [ "Spatial resolution improves, SNR decreases, and scan time doubles", "Scan time is halved", "Only the frequency resolution changes", "SNR increases and resolution decreases" ], "answer_index": 0, "explanation": "More phase steps mean smaller voxels and lower SNR, and scan time rises in proportion to phase steps.", "subcategory": "Sequence Parameters and Options" }, { "q": "What is the main benefit of a rectangular (asymmetric) FOV for an axial lumbar spine?", "options": [ "It increases SNR", "It reduces the number of phase-encoding steps, shortening scan time while keeping resolution", "It eliminates the need for saturation bands", "It removes chemical shift artifact" ], "answer_index": 1, "explanation": "With fewer phase lines covering the narrower dimension, the scan is shorter at the same voxel size, though SNR falls somewhat.", "subcategory": "Sequence Parameters and Options" }, { "q": "Why is STIR not used for fat suppression after gadolinium injection?", "options": [ "Gadolinium raises the T1 of fat", "Enhancing tissue, with its shortened T1, may be nulled along with fat", "STIR cannot be performed at 1.5 T", "STIR increases gadolinium's SAR" ], "answer_index": 1, "explanation": "STIR nulls signal by T1, not frequency, so tissue whose T1 is shortened toward that of fat can lose signal.", "subcategory": "Sequence Parameters and Options" }, { "q": "At 1.5 T, which inversion time range is typical for FLAIR?", "options": [ "About 150 ms", "About 2,000-2,500 ms", "About 500 ms", "About 5,000-6,000 ms" ], "answer_index": 1, "explanation": "FLAIR uses a long TI near the null point of CSF, roughly 2,000-2,500 ms at 1.5 T.", "subcategory": "Sequence Parameters and Options" }, { "q": "Which images does a two-point Dixon acquisition provide?", "options": [ "Only fat-suppressed T2 images", "Pre- and post-contrast subtraction images", "Diffusion and ADC maps", "In-phase, opposed-phase, water-only, and fat-only images" ], "answer_index": 3, "explanation": "Dixon combines in-phase and opposed-phase echoes to calculate separate water and fat images.", "subcategory": "Sequence Parameters and Options" }, { "q": "What is the main purpose of a spatial presaturation band placed outside the FOV?", "options": [ "To suppress signal from inflowing blood or moving tissue that would cause artifacts", "To raise the center frequency", "To shorten TE", "To increase SNR in the FOV" ], "answer_index": 0, "explanation": "Saturating spins before they enter the slice reduces flow and motion ghosting.", "subcategory": "Sequence Parameters and Options" }, { "q": "What is gradient moment nulling (flow compensation) used for?", "options": [ "Reducing phase artifacts from flowing spins moving at constant velocity", "Reducing SAR", "Removing chemical shift artifact", "Eliminating aliasing" ], "answer_index": 0, "explanation": "Extra gradient lobes rephase moving spins, but they lengthen the minimum TE.", "subcategory": "Sequence Parameters and Options" }, { "q": "What happens as the b-value in diffusion-weighted imaging increases?", "options": [ "SNR increases", "Diffusion weighting increases and SNR decreases", "Diffusion weighting decreases", "T1 weighting increases" ], "answer_index": 1, "explanation": "Higher b-values use stronger diffusion gradients, emphasizing restricted diffusion but lowering signal.", "subcategory": "Sequence Parameters and Options" }, { "q": "Why is a magnetization transfer pulse often added to 3D time-of-flight MRA of the brain?", "options": [ "To suppress background brain tissue so small vessels stand out", "To brighten the venous sinuses", "To remove the need for flow compensation", "To reduce SAR" ], "answer_index": 0, "explanation": "MT saturates macromolecule-bound protons in brain tissue, lowering background signal while blood is mostly unaffected.", "subcategory": "Sequence Parameters and Options" }, { "q": "How should the velocity encoding (VENC) be set for a phase-contrast flow study?", "options": [ "Slightly above the highest expected velocity", "At the Larmor frequency", "Well below the expected velocity", "At exactly zero" ], "answer_index": 0, "explanation": "If VENC is below the peak velocity, aliasing occurs; setting it far too high reduces velocity sensitivity.", "subcategory": "Sequence Parameters and Options" }, { "q": "What determines contrast in balanced steady-state free precession images?", "options": [ "T1 only", "Proton density only", "Diffusion", "The T2/T1 ratio" ], "answer_index": 3, "explanation": "Balanced SSFP contrast depends on T2/T1, so fluid and blood are bright, which suits cine cardiac imaging.", "subcategory": "Sequence Parameters and Options" }, { "q": "What is a key advantage of 3D volume acquisition over 2D multislice imaging?", "options": [ "No need for phase encoding", "Thin contiguous slices with higher SNR that can be reformatted in any plane", "Shorter scan times for every protocol", "No sensitivity to motion" ], "answer_index": 1, "explanation": "Exciting the whole volume gives higher SNR and isotropic voxels suitable for reformats.", "subcategory": "Sequence Parameters and Options" }, { "q": "Why is an interslice gap or interleaved slice order used in 2D multislice spin-echo imaging?", "options": [ "To shorten TE", "To reduce cross-talk between adjacent slices", "To increase spatial resolution", "To reduce gradient noise" ], "answer_index": 1, "explanation": "Imperfect slice profiles excite neighboring slices; a gap or interleaving reduces that saturation.", "subcategory": "Sequence Parameters and Options" }, { "q": "In a 2D multislice spin-echo sequence, how can more slices be acquired in one acquisition?", "options": [ "Decrease the FOV", "Decrease the TR", "Increase the TR", "Increase the NEX" ], "answer_index": 2, "explanation": "The number of slices that fit is limited by how many can be excited within each TR, so a longer TR allows more.", "subcategory": "Sequence Parameters and Options" }, { "q": "On axial lumbar spine images, pulsation ghosts from the aorta overlie the spinal canal. Which change moves the artifact off the canal?", "options": [ "Lower the receiver bandwidth", "Increase the slice thickness", "Swap the phase- and frequency-encoding directions", "Increase the TE" ], "answer_index": 2, "explanation": "Pulsatile ghosts propagate along the phase direction; changing that direction moves them away from the anatomy of interest.", "subcategory": "Sequence Parameters and Options" }, { "q": "What information is stored mainly in the outer periphery of k-space?", "options": [ "Fat-water phase information", "Overall signal intensity", "Overall image contrast", "Fine detail and edges (spatial resolution)" ], "answer_index": 3, "explanation": "High spatial frequencies sit at the periphery of k-space and define sharp edges and small structures.", "subcategory": "Data Acquisition, Processing, and Storage" }, { "q": "Which mathematical process converts raw k-space data into an image?", "options": [ "Filtered back-projection", "Fourier transform", "Bilinear interpolation", "Maximum intensity projection" ], "answer_index": 1, "explanation": "The Fourier transform turns frequency and phase information into spatial pixel intensities.", "subcategory": "Data Acquisition, Processing, and Storage" }, { "q": "What does partial Fourier (half-NEX) acquisition do?", "options": [ "Doubles the number of signal averages", "Acquires just over half of the phase lines and uses k-space symmetry to fill the rest, reducing time at the cost of SNR", "Increases spatial resolution without changing scan time", "Removes the need for phase encoding" ], "answer_index": 1, "explanation": "Conjugate symmetry lets the missing lines be estimated, shortening the scan but lowering SNR.", "subcategory": "Data Acquisition, Processing, and Storage" }, { "q": "According to the Nyquist theorem, what is the minimum sampling rate needed to represent a signal accurately?", "options": [ "Half the highest frequency", "Four times the lowest frequency", "Twice the highest frequency in the signal", "Equal to the highest frequency" ], "answer_index": 2, "explanation": "Sampling at less than twice the highest frequency causes those frequencies to be misrepresented (aliasing).", "subcategory": "Data Acquisition, Processing, and Storage" }, { "q": "What does zero-filling (zero interpolation) of k-space do?", "options": [ "Increases SNR by adding new data", "Improves apparent image smoothness and pixel size without adding true resolution", "Shortens the scan time", "Reduces SAR" ], "answer_index": 1, "explanation": "Padding k-space with zeros interpolates the image to a finer pixel grid, but no new spatial information is acquired.", "subcategory": "Data Acquisition, Processing, and Storage" }, { "q": "Fine parallel lines appear next to the cervical spinal cord on sagittal images, mimicking a syrinx. Which change reduces this truncation (Gibbs) artifact?", "options": [ "Use a larger flip angle", "Decrease the receiver bandwidth", "Increase slice thickness", "Increase the matrix in the affected direction" ], "answer_index": 3, "explanation": "Truncation artifact comes from undersampling high spatial frequencies at sharp boundaries; more sampling reduces it.", "subcategory": "Data Acquisition, Processing, and Storage" }, { "q": "A narrow line of noise runs across the image at one point in the frequency direction. What is the most likely cause?", "options": [ "Magnetic susceptibility from a dental filling", "Chemical shift", "RF interference, such as the scan room door being open", "Patient motion" ], "answer_index": 2, "explanation": "A zipper artifact at a fixed frequency points to outside RF entering through a broken RF shield or open door.", "subcategory": "Data Acquisition, Processing, and Storage" }, { "q": "In which direction does motion artifact (ghosting) propagate?", "options": [ "The frequency-encoding direction", "The slice-select direction only", "Equally in all directions", "The phase-encoding direction" ], "answer_index": 3, "explanation": "Phase encoding is acquired over a long period, so motion between phase steps creates ghosts along that axis.", "subcategory": "Data Acquisition, Processing, and Storage" }, { "q": "What is the main advantage of a phased-array coil?", "options": [ "High SNR of small coil elements combined with larger coverage", "It reduces scan time without parallel imaging", "It transmits RF for the whole body", "It eliminates the need for shimming" ], "answer_index": 0, "explanation": "Multiple small elements each with their own receiver channel give surface-coil SNR over a wide area and enable parallel imaging.", "subcategory": "Data Acquisition, Processing, and Storage" }, { "q": "How does the SNR of a surface coil change with depth into the patient?", "options": [ "It increases with depth", "It is highest at the center of the body", "It falls off with distance from the coil", "It is uniform at all depths" ], "answer_index": 2, "explanation": "Surface coils are most sensitive near the coil, so deep structures receive less signal.", "subcategory": "Data Acquisition, Processing, and Storage" }, { "q": "Using SENSE-type parallel imaging, a band of aliasing appears in the middle of the image. What is the most likely cause?", "options": [ "The patient was positioned at isocenter", "The TE was too short", "The receiver bandwidth was too wide", "The reduced FOV is smaller than the anatomy, so the unfolding fails" ], "answer_index": 3, "explanation": "Image-domain parallel imaging needs the FOV to cover the anatomy; otherwise residual aliasing appears centrally.", "subcategory": "Data Acquisition, Processing, and Storage" }, { "q": "What makes compressed sensing reconstruction possible?", "options": [ "Doubling the NEX", "Using a single-channel coil", "Fully sampling the outer k-space only", "Incoherent (pseudo-random) undersampling of k-space combined with iterative reconstruction" ], "answer_index": 3, "explanation": "Compressed sensing uses image sparsity to reconstruct images from incoherently undersampled data, reducing scan time.", "subcategory": "Data Acquisition, Processing, and Storage" }, { "q": "How does a maximum intensity projection (MIP) image work?", "options": [ "It shows the brightest voxel along each projection ray through the volume", "It averages all voxels along each ray", "It shows the darkest voxel along each ray", "It subtracts pre-contrast from post-contrast images" ], "answer_index": 0, "explanation": "MIP is used in MRA because bright vessels dominate each ray, producing an angiographic display.", "subcategory": "Data Acquisition, Processing, and Storage" }, { "q": "Which standard governs the format and transmission of medical images between scanners and PACS?", "options": [ "HIPAA", "JPEG", "DICOM", "HL7 only" ], "answer_index": 2, "explanation": "DICOM defines how medical images and their data are stored and exchanged; HL7 handles text-based clinical messages.", "subcategory": "Data Acquisition, Processing, and Storage" }, { "q": "On post-contrast subtraction images of the breast, bright and dark edges outline the skin. What is the most likely cause?", "options": [ "An incorrect VENC setting", "Too low a dose of gadolinium", "Excessive receiver bandwidth", "Patient motion between pre- and post-contrast acquisitions (misregistration)" ], "answer_index": 3, "explanation": "Subtraction assumes identical positioning; movement leaves edge artifacts where structures no longer overlap.", "subcategory": "Data Acquisition, Processing, and Storage" }, { "q": "What is the purpose of shimming?", "options": [ "To increase gradient slew rate", "To align the patient with the laser lights", "To calibrate RF power for SAR", "To improve homogeneity of the main magnetic field" ], "answer_index": 3, "explanation": "Shimming corrects B0 inhomogeneity, improving fat suppression and reducing susceptibility-related distortion.", "subcategory": "Data Acquisition, Processing, and Storage" }, { "q": "During prescan (calibration), which settings are established?", "options": [ "Window width and level", "Center frequency, transmitter gain (flip-angle calibration), and receiver gain", "Patient weight and height", "TR, TE, and slice thickness" ], "answer_index": 1, "explanation": "Prescan tunes the system to the patient's resonant frequency and sets RF transmit and receive levels.", "subcategory": "Data Acquisition, Processing, and Storage" }, { "q": "A 3 T abdominal image of a patient with large-volume ascites shows dark shading in the center of the abdomen. What is the cause and remedy?", "options": [ "Zipper artifact; close the door", "Chemical shift; increase the bandwidth", "Dielectric (standing-wave) effect from B1 inhomogeneity; use a dielectric pad or multichannel RF transmit", "Aliasing; increase the FOV" ], "answer_index": 2, "explanation": "At 3 T the RF wavelength in tissue approaches body size, creating uneven B1; dielectric pads and parallel transmit help.", "subcategory": "Data Acquisition, Processing, and Storage" }, { "q": "A 3D gradient-echo sequence uses TR 5 ms, 256 phase steps, 100 slice partitions, and NEX 1. What is the scan time?", "options": [ "2 min 8 s", "12.8 s", "1.28 s", "21 min 20 s" ], "answer_index": 0, "explanation": "3D scan time = TR x phase steps x partitions x NEX = 5 ms x 256 x 100 = 128,000 ms = 128 s.", "subcategory": "Data Acquisition, Processing, and Storage" }, { "q": "Immediately after a 180-degree inversion pulse is applied to fully relaxed tissue, what is the longitudinal magnetization?", "options": [ "Zero, with all magnetization transverse", "Half magnitude, pointing along +z", "Full magnitude, pointing along -z", "Full magnitude, rotating in the xy plane" ], "answer_index": 2, "explanation": "An inversion pulse flips Mz from +z to -z without creating transverse magnetization; it then recovers through zero by T1.", "subcategory": "Physical Principles of Image Formation" }, { "q": "Before any RF pulse is applied, how is the net magnetization vector of a patient in the bore oriented?", "options": [ "Along the longitudinal (z) axis, parallel to B0", "In the transverse (xy) plane, rotating at the Larmor frequency", "Randomly, with no net orientation in any direction", "Antiparallel to B0, pointing toward the patient's feet" ], "answer_index": 0, "explanation": "At equilibrium a small excess of low-energy spins aligns with B0, giving a net longitudinal magnetization along z.", "subcategory": "Physical Principles of Image Formation" }, { "q": "At 1.5 T and body temperature, roughly how large is the excess of low-energy (parallel) protons over high-energy protons?", "options": [ "About 5 per thousand protons", "About 5 per million protons", "About half of all protons", "About 5 per billion protons" ], "answer_index": 1, "explanation": "The Boltzmann excess is only a few parts per million at clinical field strengths, which is why MR signal is inherently weak.", "subcategory": "Physical Principles of Image Formation" }, { "q": "Why does net magnetization grow as main field strength increases?", "options": [ "The gyromagnetic ratio of hydrogen increases with field strength", "More hydrogen nuclei become MR active at stronger fields", "The energy gap widens, so more spins favor the low-energy state", "Protons precess more slowly, so fewer spins are lost to dephasing" ], "answer_index": 2, "explanation": "A stronger B0 increases the energy difference between spin states, enlarging the Boltzmann excess and the net magnetization.", "subcategory": "Physical Principles of Image Formation" }, { "q": "Which two properties of an RF pulse determine the flip angle it produces?", "options": [ "The amplitude of B1 and the pulse duration", "The main field strength and the coil size", "The receiver bandwidth and the TR", "The slice-select gradient strength and TE" ], "answer_index": 0, "explanation": "Flip angle is proportional to the B1 amplitude multiplied by the time the pulse is applied.", "subcategory": "Physical Principles of Image Formation" }, { "q": "Immediately after a 90-degree excitation pulse, how are the precessing transverse spins related to one another?", "options": [ "They have returned to the z axis", "They precess in phase (coherently)", "They are completely dephased", "They precess at random frequencies" ], "answer_index": 1, "explanation": "Excitation tips the magnetization and brings spins into phase coherence, which is what creates a measurable signal.", "subcategory": "Physical Principles of Image Formation" }, { "q": "Which physical law explains how the precessing magnetization creates a voltage in the receiver coil?", "options": [ "The inverse square law of radiation", "Ohm's law of electrical resistance", "Coulomb's law of electrostatic force", "Faraday's law of electromagnetic induction" ], "answer_index": 3, "explanation": "A changing magnetic flux through a conductor induces a voltage, so rotating transverse magnetization induces the MR signal.", "subcategory": "Physical Principles of Image Formation" }, { "q": "Which component of magnetization can be detected as MR signal by the receiver coil?", "options": [ "Magnetization in the transverse (xy) plane", "Magnetization of fully saturated spins", "Magnetization antiparallel to B0", "Magnetization aligned along the z axis" ], "answer_index": 0, "explanation": "Only rotating transverse magnetization produces a changing flux in the coil; static longitudinal magnetization induces no signal.", "subcategory": "Physical Principles of Image Formation" }, { "q": "During T1 (spin-lattice) relaxation, where does the energy absorbed from the RF pulse go?", "options": [ "It is transferred to the gradient coils", "It is converted into transverse magnetization", "It is released to the surrounding molecular lattice", "It is re-emitted as a second RF pulse" ], "answer_index": 2, "explanation": "T1 recovery occurs as excited nuclei give up energy to their molecular environment and return to the low-energy state.", "subcategory": "Physical Principles of Image Formation" }, { "q": "After an excitation that leaves no longitudinal magnetization, about how much has recovered after a time equal to three T1 values?", "options": [ "About 63%", "About 99%", "About 95%", "About 86%" ], "answer_index": 2, "explanation": "Recovery follows 1 - e^(-t/T1); at t = 3 T1 that is 1 - 0.05, or about 95%.", "subcategory": "Physical Principles of Image Formation" }, { "q": "After a time equal to two T2 values, approximately what fraction of the initial transverse magnetization remains?", "options": [ "About 50%", "About 37%", "About 5%", "About 14%" ], "answer_index": 3, "explanation": "Transverse decay follows e^(-t/T2); e^-2 is about 0.135, so roughly 14% remains.", "subcategory": "Physical Principles of Image Formation" }, { "q": "Which tissue has the longest T1 relaxation time?", "options": [ "Bone marrow fat", "White matter", "Cerebrospinal fluid", "Subcutaneous fat" ], "answer_index": 2, "explanation": "Free fluid such as CSF has the longest T1, which is why it is dark on T1-weighted images.", "subcategory": "Physical Principles of Image Formation" }, { "q": "T2 relaxation results mainly from which process?", "options": [ "Energy loss from nuclei to the receiver coil", "Recovery of magnetization along the z axis", "Gradient pulses applied during readout", "Interactions between neighboring spins' magnetic fields" ], "answer_index": 3, "explanation": "Spin-spin (dipole-dipole) interactions cause random frequency differences that dephase spins irreversibly.", "subcategory": "Physical Principles of Image Formation" }, { "q": "Which expression correctly relates T2* to T2 and field inhomogeneity (ΔB0)?", "options": [ "1/T2* = 1/T2 + γΔB0", "T2* = T2 x γΔB0", "1/T2* = 1/T2 - γΔB0", "T2* = T2 + γΔB0" ], "answer_index": 0, "explanation": "Inhomogeneity adds an extra dephasing rate to the intrinsic T2 rate, so T2* is always shorter than T2.", "subcategory": "Physical Principles of Image Formation" }, { "q": "Why does free water have a long T1 relaxation time?", "options": [ "Its molecules tumble at exactly the Larmor frequency", "It contains fewer hydrogen nuclei than fat", "Its molecules tumble much faster than the Larmor frequency", "It is strongly paramagnetic" ], "answer_index": 2, "explanation": "Energy exchange is most efficient when molecular motion is near the Larmor frequency; small, rapidly tumbling water molecules relax slowly.", "subcategory": "Physical Principles of Image Formation" }, { "q": "Why does cortical bone appear dark on essentially all conventional sequences?", "options": [ "It has a very long T1 and long T2", "Its protons precess at the fat frequency", "It has few mobile protons and an extremely short T2", "It is ferromagnetic and causes a signal void" ], "answer_index": 2, "explanation": "Cortical bone's bound protons decay before a conventional echo can be recorded, and its mobile proton density is low.", "subcategory": "Physical Principles of Image Formation" }, { "q": "Highly concentrated gadolinium pooled in the dependent bladder appears dark on a T1-weighted image. Why?", "options": [ "T1 is lengthened at high concentration", "T2/T2* shortening dominates at high concentration", "Gadolinium has no effect on urine protons", "Gadolinium is ferromagnetic in large amounts" ], "answer_index": 1, "explanation": "At high concentrations gadolinium's T2* shortening overwhelms its T1 effect, so signal drops.", "subcategory": "Physical Principles of Image Formation" }, { "q": "In a spin-echo sequence, the 180-degree pulse is applied 40 ms after the 90-degree pulse. What is the TE?", "options": [ "20 ms", "80 ms", "120 ms", "40 ms" ], "answer_index": 1, "explanation": "The echo forms at the same interval after the 180-degree pulse as the 90-to-180 interval, so TE = 2 x 40 ms.", "subcategory": "Physical Principles of Image Formation" }, { "q": "In a gradient-echo sequence, how is the echo produced?", "options": [ "By applying an inversion pulse before excitation", "By switching off the slice-select gradient", "By applying a 180-degree refocusing RF pulse", "By reversing the polarity of the readout gradient" ], "answer_index": 3, "explanation": "A dephasing gradient lobe followed by an opposite-polarity lobe rephases spins to form the gradient echo.", "subcategory": "Physical Principles of Image Formation" }, { "q": "How does the phase-encoding gradient change from one TR to the next in a 2D Cartesian acquisition?", "options": [ "It is switched on only during the RF pulse", "Its amplitude is stepped to a new value", "Its timing moves to the end of the readout", "Its polarity stays fixed and amplitude constant" ], "answer_index": 1, "explanation": "Each TR uses a different phase-encoding amplitude, filling a different line of k-space.", "subcategory": "Physical Principles of Image Formation" }, { "q": "What does the gradient slew rate describe?", "options": [ "The rate at which RF energy is deposited in tissue", "How fast a gradient can reach its peak amplitude", "The maximum strength of the main magnetic field", "The number of gradient coils in the system" ], "answer_index": 1, "explanation": "Slew rate (T/m/s) is peak gradient amplitude divided by rise time; higher slew rates allow faster sequences.", "subcategory": "Physical Principles of Image Formation" }, { "q": "A 10 mT/m gradient is on. How much higher is the precessional frequency of protons 10 cm from isocenter on the positive side?", "options": [ "About 42.6 kHz", "About 426 Hz", "About 426 kHz", "About 4.26 kHz" ], "answer_index": 0, "explanation": "The extra field is 10 mT/m x 0.1 m = 1 mT, and 42.58 MHz/T x 0.001 T is about 42.6 kHz.", "subcategory": "Physical Principles of Image Formation" }, { "q": "An RF pulse with a bandwidth of 2,130 Hz is applied with a 10 mT/m slice-select gradient. What slice thickness results?", "options": [ "About 5 mm", "About 10 mm", "About 2.5 mm", "About 0.5 mm" ], "answer_index": 0, "explanation": "The gradient creates 42.58 kHz/mT x 10 mT/m, or about 426 Hz/mm, so 2,130 Hz covers about 5 mm.", "subcategory": "Physical Principles of Image Formation" }, { "q": "With the slice-select gradient on, how does the scanner choose which slice location is excited?", "options": [ "By changing the receiver bandwidth", "By changing the flip angle", "By shifting the center frequency of the RF pulse", "By moving the table during excitation" ], "answer_index": 2, "explanation": "Each position along the gradient has its own Larmor frequency, so the RF center frequency selects the slice location.", "subcategory": "Physical Principles of Image Formation" }, { "q": "On a magnitude-reconstructed inversion-recovery image, how is a tissue with negative longitudinal magnetization displayed?", "options": [ "As inverted gray, darker than background", "As a phase-wrapped artifact", "As black, because negative values are set to zero", "As positive signal, because its sign is discarded" ], "answer_index": 3, "explanation": "Magnitude reconstruction ignores sign, so tissues below the null point appear bright; phase-sensitive IR preserves the sign.", "subcategory": "Physical Principles of Image Formation" }, { "q": "On an axial gradient-echo image, a thin black line outlines every boundary where fat and water share a voxel, in all directions. What is this?", "options": [ "Chemical shift artifact of the first kind", "Zipper artifact from RF leakage", "Gibbs truncation artifact", "Chemical shift artifact of the second kind" ], "answer_index": 3, "explanation": "At opposed-phase TEs, fat and water signals cancel in mixed voxels, producing a dark India-ink outline independent of encoding direction.", "subcategory": "Physical Principles of Image Formation" }, { "q": "Which material is diamagnetic?", "options": [ "Water", "Gadolinium", "Deoxyhemoglobin", "Iron oxide" ], "answer_index": 0, "explanation": "Most tissues and water are weakly diamagnetic; gadolinium and deoxyhemoglobin are paramagnetic and iron oxide is superparamagnetic.", "subcategory": "Physical Principles of Image Formation" }, { "q": "For a spoiled gradient echo where e^(-TR/T1) equals 0.5, what flip angle (Ernst angle) gives maximum signal?", "options": [ "60 degrees", "45 degrees", "90 degrees", "30 degrees" ], "answer_index": 0, "explanation": "The Ernst angle satisfies cos θ = e^(-TR/T1); cos θ = 0.5 gives 60 degrees.", "subcategory": "Physical Principles of Image Formation" }, { "q": "Why is hydrogen the nucleus used for clinical MR imaging?", "options": [ "It is the only nucleus with an even number of protons", "It precesses at the same frequency as all other nuclei", "It is abundant in the body and has a large magnetic moment", "It has no gyromagnetic ratio, so it is stable" ], "answer_index": 2, "explanation": "Hydrogen's single proton gives a strong magnetic moment and it is plentiful in water and fat, yielding the most signal.", "subcategory": "Physical Principles of Image Formation" }, { "q": "Which nucleus is NOT MR active?", "options": [ "Carbon-12", "Phosphorus-31", "Fluorine-19", "Sodium-23" ], "answer_index": 0, "explanation": "MR-active nuclei have an odd number of protons and/or neutrons; carbon-12 has six of each and no net spin.", "subcategory": "Physical Principles of Image Formation" }, { "q": "A slice receives many RF pulses with a TR much shorter than its T1. What happens to its signal?", "options": [ "It decreases because the tissue becomes partially saturated", "It becomes negative and is displayed as black", "It increases because more spins are excited", "It is unchanged because T1 has no effect on signal" ], "answer_index": 0, "explanation": "With little time to recover between pulses, longitudinal magnetization stays low, so each excitation produces less signal.", "subcategory": "Physical Principles of Image Formation" }, { "q": "A 1.5 T magnet has a homogeneity of 1 ppm over its imaging volume. What frequency spread does this represent?", "options": [ "About 1.5 Hz", "About 64 Hz", "About 6.4 Hz", "About 640 Hz" ], "answer_index": 1, "explanation": "One part per million of 63.86 MHz is about 64 Hz.", "subcategory": "Physical Principles of Image Formation" }, { "q": "What is the magnet isocenter?", "options": [ "The location of the 5-gauss line", "The point where all three gradient fields equal zero", "The center of the receiver coil only", "The edge of the bore where fringe field is highest" ], "answer_index": 1, "explanation": "At isocenter none of the gradients add to or subtract from B0, so protons precess at the base Larmor frequency.", "subcategory": "Physical Principles of Image Formation" }, { "q": "Hydrogen has a spin quantum number of 1/2. How many energy states can its protons occupy in a magnetic field?", "options": [ "Three", "Two", "Four", "One" ], "answer_index": 1, "explanation": "A nucleus with spin I has 2I + 1 states, so hydrogen has two: parallel (low energy) and antiparallel (high energy).", "subcategory": "Physical Principles of Image Formation" }, { "q": "If the duration of an RF pulse is shortened while its shape is kept the same, what happens to its frequency bandwidth?", "options": [ "It drops to zero", "It becomes wider", "It becomes narrower", "It is unchanged" ], "answer_index": 1, "explanation": "Time and frequency are inversely related, so a shorter pulse contains a broader range of frequencies.", "subcategory": "Physical Principles of Image Formation" }, { "q": "Why is a sinc-shaped RF pulse commonly used for slice selection?", "options": [ "It produces a nearly rectangular slice profile", "It excites only fat protons in the slice", "It deposits no RF energy in the patient", "It eliminates the need for a slice-select gradient" ], "answer_index": 0, "explanation": "The Fourier transform of a sinc is a rectangle, so a sinc pulse excites a well-defined band of frequencies.", "subcategory": "Physical Principles of Image Formation" }, { "q": "How is the B1 field of the RF transmit coil oriented relative to the main field B0?", "options": [ "Antiparallel to B0", "Parallel to B0", "Perpendicular to B0", "At the magic angle to B0" ], "answer_index": 2, "explanation": "A B1 field perpendicular to B0 is needed to tip the magnetization away from the z axis.", "subcategory": "Physical Principles of Image Formation" }, { "q": "In a rotating frame of reference turning at the Larmor frequency, how do on-resonance spins appear?", "options": [ "Rotating in the opposite direction", "Moving randomly", "Rotating at twice the Larmor frequency", "Stationary" ], "answer_index": 3, "explanation": "Viewing spins in a frame rotating at their own frequency removes the precession, simplifying description of the RF pulse effect.", "subcategory": "Physical Principles of Image Formation" }, { "q": "Why do fat protons resonate at a slightly lower frequency than water protons?", "options": [ "They are located farther from isocenter", "They have a different gyromagnetic ratio", "Their electron cloud shields them more from B0", "They have a longer T1 relaxation time" ], "answer_index": 2, "explanation": "Greater electron shielding in fat's hydrocarbon chains lowers the local field the protons feel, about 3.5 ppm below water.", "subcategory": "Physical Principles of Image Formation" }, { "q": "Which hemoglobin breakdown product is diamagnetic and therefore causes little susceptibility effect?", "options": [ "Methemoglobin", "Deoxyhemoglobin", "Oxyhemoglobin", "Hemosiderin" ], "answer_index": 2, "explanation": "Oxyhemoglobin has no unpaired electrons; deoxyhemoglobin, methemoglobin and hemosiderin are paramagnetic or superparamagnetic.", "subcategory": "Physical Principles of Image Formation" }, { "q": "A sequence uses a 240 mm FOV with a 256 x 256 matrix. What is the in-plane pixel size?", "options": [ "About 0.94 mm", "About 1.88 mm", "About 1.07 mm", "About 0.47 mm" ], "answer_index": 0, "explanation": "Pixel size equals FOV divided by matrix: 240 mm / 256 is about 0.94 mm.", "subcategory": "Sequence Parameters and Options" }, { "q": "A 256 mm FOV is acquired with a 256 (frequency) x 128 (phase) matrix and 5 mm slices. What is the voxel volume?", "options": [ "20 mm³", "2.5 mm³", "10 mm³", "5 mm³" ], "answer_index": 2, "explanation": "Voxel dimensions are 1 mm x 2 mm x 5 mm, giving 10 mm³.", "subcategory": "Sequence Parameters and Options" }, { "q": "A conventional spin-echo sequence uses TR 600 ms, 192 phase-encoding steps, and NEX 2. What is the scan time?", "options": [ "About 3 min 50 s", "About 1 min 55 s", "About 7 min 41 s", "About 38 s" ], "answer_index": 0, "explanation": "Scan time = TR x phase steps x NEX = 0.6 s x 192 x 2 = 230.4 s, about 3 min 50 s.", "subcategory": "Sequence Parameters and Options" }, { "q": "Starting from NEX 1, what NEX is needed to double SNR when no other parameter is changed?", "options": [ "NEX 8", "NEX 3", "NEX 4", "NEX 2" ], "answer_index": 2, "explanation": "SNR scales with the square root of NEX, so doubling SNR requires four times the averages and four times the time.", "subcategory": "Sequence Parameters and Options" }, { "q": "The frequency matrix is increased from 256 to 512 with phase steps, TR, and NEX unchanged. What happens to scan time?", "options": [ "It doubles", "It does not change", "It quadruples", "It is halved" ], "answer_index": 1, "explanation": "Scan time depends on TR, phase steps and NEX, not on the number of frequency samples; SNR per voxel falls instead.", "subcategory": "Sequence Parameters and Options" }, { "q": "Fat stays bright on fast spin-echo T2-weighted images compared with conventional spin echo. What explains this?", "options": [ "Closely spaced 180° pulses disrupt J-coupling in fat", "The fat-water chemical shift is larger in FSE", "Fat has a longer T2 at higher field strengths", "FSE uses a shorter TR than conventional SE" ], "answer_index": 0, "explanation": "Rapid refocusing pulses suppress J-coupling dephasing among fat protons, so fat signal decays less on FSE.", "subcategory": "Sequence Parameters and Options" }, { "q": "An FSE image of the knee looks blurred. Which change most directly reduces this blurring?", "options": [ "Reducing the receiver bandwidth", "Shortening the echo spacing", "Increasing the TR", "Lengthening the echo train" ], "answer_index": 1, "explanation": "Blurring comes from T2 decay across the echo train; shorter echo spacing (or a shorter train) reduces signal modulation in k-space.", "subcategory": "Sequence Parameters and Options" }, { "q": "What characterizes a single-shot half-Fourier FSE (HASTE/SSFSE) acquisition?", "options": [ "Each k-space line requires its own excitation and TR", "It requires a breath-hold of several minutes per slice", "All needed k-space lines for a slice follow one excitation", "It uses only gradient echoes with no 180° pulses" ], "answer_index": 2, "explanation": "One excitation and a long echo train fill about half of k-space, freezing motion at the cost of some blurring.", "subcategory": "Sequence Parameters and Options" }, { "q": "In a driven-equilibrium FSE (e.g., DRIVE, FRFSE), what is added at the end of the echo train?", "options": [ "A fat-selective saturation pulse", "A spoiler gradient that destroys all magnetization", "A second 90° excitation in the same direction", "A -90° pulse that returns transverse magnetization to the z axis" ], "answer_index": 3, "explanation": "The flip-back pulse restores longitudinal magnetization, allowing bright fluid with a shorter TR.", "subcategory": "Sequence Parameters and Options" }, { "q": "How does double inversion recovery produce black-blood cardiac images?", "options": [ "Gadolinium is injected to darken the blood pool", "Two 90° pulses dephase stationary myocardium", "A fat-selective pulse saturates fat in blood", "A nonselective inversion followed by slice-selective reinversion nulls inflowing blood" ], "answer_index": 3, "explanation": "Blood outside the slice stays inverted and flows in at its null point, while myocardium in the slice is restored.", "subcategory": "Sequence Parameters and Options" }, { "q": "How does chemically selective fat saturation (CHESS) suppress fat?", "options": [ "The receiver bandwidth is narrowed to exclude fat", "Fat and water images are calculated from two echoes", "An inversion pulse nulls all short-T1 tissue", "A pulse at the fat frequency excites fat, then a spoiler dephases it" ], "answer_index": 3, "explanation": "Fat is excited selectively and its transverse magnetization is spoiled just before the imaging excitation.", "subcategory": "Sequence Parameters and Options" }, { "q": "What does water-excitation fat suppression do?", "options": [ "It inverts all tissue and images at the fat null point", "It uses spectral-spatial pulses that excite only water protons", "It subtracts an out-of-phase image from an in-phase image", "It saturates everything outside the FOV" ], "answer_index": 1, "explanation": "Composite (binomial) pulses tip water into the transverse plane while leaving fat near the z axis.", "subcategory": "Sequence Parameters and Options" }, { "q": "How do 'quiet' or 'silent' sequence options reduce acoustic noise?", "options": [ "By using a narrower receiver bandwidth only", "By raising the RF flip angle on every pulse", "By switching off the main magnetic field", "By softening gradient ramps and lowering slew rates" ], "answer_index": 3, "explanation": "Acoustic noise comes from rapidly switched gradients vibrating in B0, so gentler gradient waveforms make scanning quieter.", "subcategory": "Sequence Parameters and Options" }, { "q": "How does echo-planar imaging (EPI) fill k-space so quickly?", "options": [ "Only the center line of k-space is ever acquired", "A rapidly oscillating readout gradient collects many lines after one excitation", "Each line is collected after a separate 90° pulse", "The phase-encoding gradient is switched off" ], "answer_index": 1, "explanation": "Alternating readout lobes with phase blips traverse k-space in tens of milliseconds, making EPI sensitive to susceptibility distortion.", "subcategory": "Sequence Parameters and Options" }, { "q": "A lesion is bright on DWI at b = 1000 and also bright on the ADC map. What is the best explanation?", "options": [ "T2 shine-through rather than restricted diffusion", "Magnetic susceptibility from calcium", "Chemical shift misregistration", "Acute restricted diffusion" ], "answer_index": 0, "explanation": "True restriction is dark on ADC; brightness on both suggests long-T2 signal carrying through the diffusion image.", "subcategory": "Sequence Parameters and Options" }, { "q": "Susceptibility-weighted imaging (SWI) combines which types of data from a 3D gradient echo?", "options": [ "In-phase and opposed-phase echoes", "Magnitude and filtered phase", "Pre-contrast and post-contrast images", "Real and imaginary k-space only" ], "answer_index": 1, "explanation": "A phase mask derived from filtered phase is multiplied into the magnitude image to accentuate susceptibility differences.", "subcategory": "Sequence Parameters and Options" }, { "q": "How does a navigator echo help in free-breathing abdominal or cardiac imaging?", "options": [ "It saturates moving tissue outside the FOV", "It averages many signals to blur out motion", "It triggers acquisition on the R-wave of the ECG", "It tracks diaphragm position and accepts data only within a set window" ], "answer_index": 3, "explanation": "A pencil-beam navigator monitors the lung-liver interface so data are kept when the diaphragm is in the chosen position.", "subcategory": "Sequence Parameters and Options" }, { "q": "When peripheral pulse gating is used instead of ECG gating, what timing difference must be considered?", "options": [ "The peripheral pulse lags the R-wave by a few hundred milliseconds", "The peripheral pulse is synchronous with the T-wave", "The peripheral pulse occurs before the P-wave", "There is no delay between the two signals" ], "answer_index": 0, "explanation": "The pressure wave reaches the finger well after ventricular depolarization, so systolic phases are harder to capture.", "subcategory": "Sequence Parameters and Options" }, { "q": "A gated spin-echo study triggers on every R-wave in a patient with a heart rate of 75 bpm. What is the effective TR?", "options": [ "750 ms", "1,333 ms", "800 ms", "1,600 ms" ], "answer_index": 2, "explanation": "The R-R interval is 60,000 ms / 75 = 800 ms, which sets the effective TR when triggering each beat.", "subcategory": "Sequence Parameters and Options" }, { "q": "Why is aliasing rarely seen in the frequency-encoding direction on modern scanners?", "options": [ "The frequency gradient is too weak to cause wrap", "Anatomy is always centered in the frequency direction", "Frequency oversampling is applied with no added scan time", "Frequency encoding uses a larger matrix by default" ], "answer_index": 2, "explanation": "Sampling the readout faster and filtering out-of-FOV frequencies prevents frequency wrap at no time cost.", "subcategory": "Sequence Parameters and Options" }, { "q": "Dark bands cross a balanced SSFP cardiac cine in a region of poor field homogeneity. Which change best reduces them?", "options": [ "Improve shimming and use the shortest possible TR", "Reduce the receiver bandwidth", "Switch to a longer echo train length", "Lengthen the TR and lower the flip angle" ], "answer_index": 0, "explanation": "bSSFP banding arises from off-resonance; better shimming and a shorter TR widen the band spacing.", "subcategory": "Sequence Parameters and Options" }, { "q": "What is the main benefit of a partial (fractional) echo readout?", "options": [ "It allows a shorter minimum TE", "It increases the number of phase steps", "It eliminates chemical shift artifact", "It doubles SNR without extra time" ], "answer_index": 0, "explanation": "Sampling only part of the echo before its peak lets the echo be centered earlier, shortening TE.", "subcategory": "Sequence Parameters and Options" }, { "q": "Besides lowering SNR, what does widening the receiver bandwidth allow?", "options": [ "More phase-encoding steps per TR", "Shorter minimum TE and echo spacing", "Longer echo trains with less blurring due to longer spacing", "Higher SNR in the phase direction" ], "answer_index": 1, "explanation": "A faster readout shortens sampling time, which permits shorter TE and tighter echo spacing in FSE.", "subcategory": "Sequence Parameters and Options" }, { "q": "What is the purpose of crusher (spoiler) gradients placed around the 180° pulse in a spin-echo sequence?", "options": [ "To increase the T1 weighting of the image", "To dephase unwanted signal from an imperfect refocusing pulse", "To encode position along the readout direction", "To refocus static field inhomogeneities" ], "answer_index": 1, "explanation": "Symmetric crushers preserve the desired echo while destroying stray FID signal generated by the 180° pulse.", "subcategory": "Sequence Parameters and Options" }, { "q": "What is an MPRAGE sequence?", "options": [ "A phase-contrast sequence for CSF flow", "A dual-echo spin echo for proton density and T2", "A single-shot EPI diffusion sequence", "An inversion-prepared rapid 3D gradient echo with strong T1 weighting" ], "answer_index": 3, "explanation": "An inversion pulse followed by a fast GRE readout yields high gray-white contrast in a 3D isotropic volume.", "subcategory": "Sequence Parameters and Options" }, { "q": "In 3D time-of-flight MRA, why does a ramped (TONE) flip angle improve distal vessel signal?", "options": [ "It lengthens TR so stationary tissue recovers", "It suppresses venous signal by inverting blood", "It shortens TE to reduce intravoxel dephasing", "The flip angle increases across the slab as inflowing blood becomes more saturated" ], "answer_index": 3, "explanation": "Lower angles at the entry side preserve blood magnetization, while higher angles distally compensate for saturation.", "subcategory": "Sequence Parameters and Options" }, { "q": "In phase-contrast MRI, the measured phase shift of moving spins is proportional to what?", "options": [ "The square of their T2", "Their velocity along the encoding direction", "Their distance from the receiver coil", "Their T1 relaxation time" ], "answer_index": 1, "explanation": "Bipolar gradients leave stationary spins unchanged and give moving spins a phase shift proportional to velocity.", "subcategory": "Sequence Parameters and Options" }, { "q": "In contrast-enhanced MRA with centric k-space ordering, when should the center of k-space be acquired?", "options": [ "After the contrast has fully washed out", "Before contrast reaches the arteries", "At peak arterial gadolinium concentration", "During peak venous enhancement" ], "answer_index": 2, "explanation": "Center-of-k-space data set image contrast, so they must coincide with the arterial bolus peak.", "subcategory": "Sequence Parameters and Options" }, { "q": "How do time-resolved MRA techniques (such as TWIST or TRICKS) achieve high frame rates?", "options": [ "Each frame uses a full new k-space acquisition", "The center of k-space is updated often while outer data are shared between frames", "The FOV is reduced to a single vessel", "Only the outer k-space lines are acquired each frame" ], "answer_index": 1, "explanation": "View sharing reuses peripheral data while frequently refreshing contrast-defining central data.", "subcategory": "Sequence Parameters and Options" }, { "q": "Which factors determine the b-value of a diffusion-weighted sequence?", "options": [ "TR, flip angle, and slice thickness", "Diffusion gradient amplitude, duration, and spacing", "Receiver bandwidth and coil type", "FOV, matrix, and NEX" ], "answer_index": 1, "explanation": "The b-value grows with the strength and length of the diffusion gradients and the time between them.", "subcategory": "Sequence Parameters and Options" }, { "q": "A 2D spin-echo sequence uses TR 500 ms, and each slice requires 25 ms of sequence time. About how many slices can be acquired in one TR?", "options": [ "40", "20", "25", "10" ], "answer_index": 1, "explanation": "The number of interleaved slices is roughly TR divided by time per slice: 500 / 25 = 20.", "subcategory": "Sequence Parameters and Options" }, { "q": "Which technique reduces metal artifact by acquiring and combining multiple off-resonance frequency bins?", "options": [ "Chemical shift selective fat saturation", "Single-shot echo-planar imaging", "Balanced steady-state free precession", "Multispectral imaging (e.g., MAVRIC, SEMAC)" ], "answer_index": 3, "explanation": "Exciting separate spectral bins captures spins shifted by the implant's field and combines them into one image.", "subcategory": "Sequence Parameters and Options" }, { "q": "What makes a gradient-echo sequence 'spoiled'?", "options": [ "A refocusing pulse is added after excitation", "Residual transverse magnetization is destroyed before each excitation", "The phase-encoding gradient is omitted", "The flip angle is fixed at 180 degrees" ], "answer_index": 1, "explanation": "RF spoiling or spoiler gradients remove leftover transverse signal so contrast is mainly T1 (or T2*) dependent.", "subcategory": "Sequence Parameters and Options" }, { "q": "A coherent steady state with residual transverse magnetization develops in gradient-echo imaging when:", "options": [ "TR is shorter than the tissue T2", "The flip angle is set to 0 degrees", "TE is longer than the TR", "TR is much longer than the tissue T1" ], "answer_index": 0, "explanation": "If TR is shorter than T2, transverse magnetization persists into the next TR and contributes to the steady state.", "subcategory": "Sequence Parameters and Options" }, { "q": "Readout-segmented EPI (e.g., RESOLVE) is used for diffusion imaging because it:", "options": [ "Removes the need for fat suppression", "Reduces distortion and blurring compared with single-shot EPI", "Allows b-values above 10,000 with no time penalty", "Eliminates the need for diffusion gradients" ], "answer_index": 1, "explanation": "Splitting the readout into segments shortens echo spacing, lowering susceptibility distortion and T2* blurring.", "subcategory": "Sequence Parameters and Options" }, { "q": "A tissue's signal is 1,000 at b = 0 and 368 at b = 1,000 s/mm². What is its approximate ADC?", "options": [ "0.63 x 10⁻³ mm²/s", "2.7 x 10⁻³ mm²/s", "0.37 x 10⁻³ mm²/s", "1.0 x 10⁻³ mm²/s" ], "answer_index": 3, "explanation": "ADC = ln(S0/Sb)/b = ln(1000/368)/1000 = 1/1000, or 1.0 x 10⁻³ mm²/s.", "subcategory": "Sequence Parameters and Options" }, { "q": "In a 2D Cartesian spin-echo acquisition, what does each line of k-space represent?", "options": [ "One column of the receiver coil", "One pixel of the final image", "One slice of the anatomy", "The echo from one phase-encoding step" ], "answer_index": 3, "explanation": "Each phase-encoding step produces an echo that is sampled and stored as one row of k-space.", "subcategory": "Data Acquisition, Processing, and Storage" }, { "q": "Which property of k-space allows only slightly more than half of it to be acquired?", "options": [ "Its logarithmic spacing", "Conjugate (Hermitian) symmetry", "Its zero center value", "Its uniform brightness" ], "answer_index": 1, "explanation": "Data in one half of k-space mirror the other half, so the missing portion can be estimated mathematically.", "subcategory": "Data Acquisition, Processing, and Storage" }, { "q": "Which phase-encoding step fills the center line of k-space?", "options": [ "The step with the largest positive amplitude", "The final step of the acquisition", "The step with the smallest (zero) gradient amplitude", "The step with the largest negative amplitude" ], "answer_index": 2, "explanation": "Weak phase encoding produces the strongest signal, which lies at the center of k-space.", "subcategory": "Data Acquisition, Processing, and Storage" }, { "q": "A readout collects 256 samples with a total receiver bandwidth of 32 kHz. How long is the sampling window?", "options": [ "8 ms", "16 ms", "4 ms", "0.8 ms" ], "answer_index": 0, "explanation": "Dwell time is 1/32,000 s, or 31.25 µs, and 256 samples take 256 x 31.25 µs = 8 ms.", "subcategory": "Data Acquisition, Processing, and Storage" }, { "q": "At 1.5 T (fat-water shift about 220 Hz), a sequence uses a ±16 kHz receiver bandwidth with 256 frequency samples. About how many pixels is fat shifted?", "options": [ "About 1.8 pixels", "About 3.5 pixels", "About 0.9 pixel", "About 7 pixels" ], "answer_index": 0, "explanation": "The total 32 kHz over 256 pixels is 125 Hz/pixel, and 220 / 125 is about 1.8 pixels.", "subcategory": "Data Acquisition, Processing, and Storage" }, { "q": "Which device converts the received MR signal into numbers stored in k-space?", "options": [ "RF power amplifier", "Digital-to-analog converter", "Gradient amplifier", "Analog-to-digital converter" ], "answer_index": 3, "explanation": "The ADC samples the analog signal at the dwell-time interval and digitizes it for storage and reconstruction.", "subcategory": "Data Acquisition, Processing, and Storage" }, { "q": "What is a key benefit of quadrature detection in the receiver?", "options": [ "It distinguishes frequencies above and below the reference frequency", "It removes all motion artifact", "It eliminates the need for a Fourier transform", "It increases the main field homogeneity" ], "answer_index": 0, "explanation": "Two channels 90° apart give real and imaginary signals, separating positive from negative offsets and improving SNR.", "subcategory": "Data Acquisition, Processing, and Storage" }, { "q": "Routine MR images display which part of the complex reconstructed data?", "options": [ "The phase only", "The imaginary part only", "The real part only", "The magnitude" ], "answer_index": 3, "explanation": "Magnitude images combine real and imaginary components and ignore phase, which is used only in special applications.", "subcategory": "Data Acquisition, Processing, and Storage" }, { "q": "In Cartesian imaging, the FOV in the phase direction is inversely related to what?", "options": [ "The highest k-space value acquired", "The amplitude of the slice-select gradient", "The spacing between adjacent k-space lines", "The total number of slices" ], "answer_index": 2, "explanation": "Larger steps between phase-encoding lines shrink the FOV; the extent of k-space sets spatial resolution.", "subcategory": "Data Acquisition, Processing, and Storage" }, { "q": "A diagonal striped (herringbone or corduroy) pattern covers an entire image. What is the most likely source?", "options": [ "Patient motion during acquisition", "Too thin a slice thickness", "A spike of bad data in k-space", "A missing gadolinium injection" ], "answer_index": 2, "explanation": "A single bright point in k-space transforms into a striped pattern across the whole image.", "subcategory": "Data Acquisition, Processing, and Storage" }, { "q": "Why is radial blade (PROPELLER/BLADE) k-space acquisition useful for restless patients?", "options": [ "It needs no gradient switching", "It acquires only the edges of k-space", "It eliminates the need for multiple coils", "Each blade passes through the center, allowing motion correction" ], "answer_index": 3, "explanation": "Oversampling the center with every rotated blade lets the scanner detect and correct in-plane motion between blades.", "subcategory": "Data Acquisition, Processing, and Storage" }, { "q": "What is a drawback of spiral k-space trajectories?", "options": [ "They always require a very long TR", "They cannot sample the center of k-space", "Blurring from off-resonance and field inhomogeneity", "They only work with spin-echo sequences" ], "answer_index": 2, "explanation": "Off-resonance errors accumulate along the spiral readout, causing blurring rather than shifts.", "subcategory": "Data Acquisition, Processing, and Storage" }, { "q": "Parallel imaging with an acceleration factor of 4 and a g-factor of 1.0 is used. Compared with the unaccelerated scan, what is the SNR?", "options": [ "Half", "Unchanged", "Double", "One quarter" ], "answer_index": 0, "explanation": "SNR drops by g x √R; with R = 4 and g = 1, SNR falls to 1/2.", "subcategory": "Data Acquisition, Processing, and Storage" }, { "q": "How does GRAPPA differ from SENSE?", "options": [ "GRAPPA needs no coil information at all", "GRAPPA restores missing lines in k-space before reconstruction", "GRAPPA works only with single-channel coils", "GRAPPA unfolds aliasing in the image domain" ], "answer_index": 1, "explanation": "GRAPPA uses autocalibration lines to synthesize missing k-space data; SENSE unfolds aliased images using coil sensitivity maps.", "subcategory": "Data Acquisition, Processing, and Storage" }, { "q": "On a PACS workstation, the window width is narrowed. What happens to the displayed image?", "options": [ "Contrast decreases and the image looks flatter", "Overall brightness rises without changing contrast", "Spatial resolution of the image improves", "Contrast increases because fewer gray levels span the range" ], "answer_index": 3, "explanation": "A narrower window spreads the display gray scale over fewer signal values, accentuating differences.", "subcategory": "Data Acquisition, Processing, and Storage" }, { "q": "Which standard is mainly used to exchange orders and reports between hospital and radiology information systems?", "options": [ "JPEG", "DICOM", "TCP/IP", "HL7" ], "answer_index": 3, "explanation": "HL7 handles text-based clinical and administrative messages, while DICOM handles images.", "subcategory": "Data Acquisition, Processing, and Storage" }, { "q": "What is true of lossless image compression?", "options": [ "The original data can be restored exactly", "Some image data are permanently discarded", "It always reduces file size by 90%", "It is not permitted for MR images" ], "answer_index": 0, "explanation": "Lossless methods reduce file size without any loss, unlike lossy compression.", "subcategory": "Data Acquisition, Processing, and Storage" }, { "q": "An image has a 512 x 512 matrix stored at 16 bits (2 bytes) per pixel. About how large is the uncompressed file?", "options": [ "About 256 KB", "About 1 MB", "About 64 KB", "About 512 KB" ], "answer_index": 3, "explanation": "512 x 512 x 2 bytes = 524,288 bytes, about 512 KB.", "subcategory": "Data Acquisition, Processing, and Storage" }, { "q": "Which projection is used on susceptibility-weighted images to display small veins as continuous dark structures?", "options": [ "Minimum intensity projection", "Volume rendering with surface shading", "Average intensity projection", "Maximum intensity projection" ], "answer_index": 0, "explanation": "MinIP keeps the lowest value along each ray, highlighting dark, low-signal veins and blood products.", "subcategory": "Data Acquisition, Processing, and Storage" }, { "q": "A smoothing filter is applied during reconstruction. What is the trade-off?", "options": [ "Scan time increases without image change", "Contrast increases but wrap appears", "Noise is increased but edges are sharper", "Noise is reduced but edges become blurred" ], "answer_index": 3, "explanation": "Low-pass filtering suppresses high-frequency noise along with high-frequency detail.", "subcategory": "Data Acquisition, Processing, and Storage" }, { "q": "In a 3D acquisition with too small a slab, wrap may occur along which directions?", "options": [ "Phase direction only", "Frequency direction only", "Phase and slice (partition) encoding directions", "No direction, because 3D cannot wrap" ], "answer_index": 2, "explanation": "Both in-plane phase and through-plane partition directions are phase encoded and can alias.", "subcategory": "Data Acquisition, Processing, and Storage" }, { "q": "A bright dot appears at the exact center of every image in a series. What is the likely cause?", "options": [ "Chemical shift of fat", "A ferromagnetic hairpin on the patient", "A DC offset in the receiver (central point artifact)", "Inadequate fat suppression" ], "answer_index": 2, "explanation": "A constant voltage offset adds a value at the center of k-space data, producing a central dot after reconstruction.", "subcategory": "Data Acquisition, Processing, and Storage" }, { "q": "Images from a surface coil are very bright near the coil and dark farther away. Which processing option corrects this?", "options": [ "Intensity normalization using a coil sensitivity reference", "Switching phase and frequency", "Increasing the ETL", "Adding a saturation band" ], "answer_index": 0, "explanation": "Normalization filters (such as prescan normalize, CLEAR, or PURE) compensate for coil sensitivity falloff.", "subcategory": "Data Acquisition, Processing, and Storage" }, { "q": "How is SNR commonly estimated on a phantom image?", "options": [ "Mean signal in an ROI divided by the standard deviation of noise", "Matrix size divided by FOV", "Peak signal minus background signal", "Window width divided by window level" ], "answer_index": 0, "explanation": "Signal ROI mean over noise SD from a background or difference image gives a reproducible SNR estimate.", "subcategory": "Data Acquisition, Processing, and Storage" }, { "q": "Data clipping and distorted images occur after prescan. What setting was most likely wrong?", "options": [ "Window level set too low", "Receiver gain set too high", "TR set too long", "Slice gap set too wide" ], "answer_index": 1, "explanation": "Excessive receiver gain saturates the ADC, clipping the strongest k-space data.", "subcategory": "Data Acquisition, Processing, and Storage" }, { "q": "Diffusion images show shearing and stretching that change with gradient direction. What is the main cause?", "options": [ "Excessive receiver bandwidth", "Patient motion in the frequency direction", "Eddy currents from the strong diffusion gradients", "Chemical shift from water" ], "answer_index": 2, "explanation": "Rapid switching of strong diffusion gradients induces eddy currents that distort EPI images in a direction-dependent way.", "subcategory": "Data Acquisition, Processing, and Storage" }, { "q": "How does a single data point in k-space relate to the final image?", "options": [ "It defines one specific pixel", "It defines one row of pixels only", "It defines the slice position only", "It contributes information to every pixel" ], "answer_index": 3, "explanation": "Each k-space point represents one spatial frequency, which is spread throughout the whole image.", "subcategory": "Data Acquisition, Processing, and Storage" }, { "q": "Under ACR MR accreditation guidance, which is a routine weekly technologist QC check?", "options": [ "Magnetic field homogeneity mapping", "Gradient coil replacement", "Center (resonance) frequency", "RF shielding effectiveness test" ], "answer_index": 2, "explanation": "Weekly technologist QC includes center frequency and phantom checks; homogeneity mapping and shielding tests are physicist or acceptance tasks.", "subcategory": "Data Acquisition, Processing, and Storage" }, { "q": "A small structure appears blurred and less conspicuous on 8 mm slices than on 3 mm slices. What is the main cause?", "options": [ "Phase-direction aliasing", "Magnetic susceptibility", "Chemical shift misregistration", "Partial-volume averaging" ], "answer_index": 3, "explanation": "Thicker voxels average the small structure with surrounding tissue, reducing its contrast and sharpness.", "subcategory": "Data Acquisition, Processing, and Storage" }, { "q": "One region of a phased-array image is markedly darker and noisier, and the coil check flags one element. What is the most likely cause?", "options": [ "Excessive fat suppression", "A failed or disconnected coil element", "Too many phase-encoding steps", "An incorrect window level" ], "answer_index": 1, "explanation": "A nonfunctioning element loses its local sensitivity, leaving a region of low signal and high noise.", "subcategory": "Data Acquisition, Processing, and Storage" } ] }, { "id": "procedures", "name": "Procedures", "main_points": [ "A routine brain exam usually includes sagittal T1, axial T2, FLAIR, DWI/ADC, and a susceptibility-sensitive sequence (GRE or SWI), with post-contrast T1 when indicated.", "MS protocols add sagittal (often 3D) FLAIR to show periventricular lesions running perpendicular to the ventricles ('Dawson's fingers'), plus post-contrast T1 to show active lesions.", "Seizure protocols use thin oblique coronal T2/FLAIR slices angled perpendicular to the long axis of the hippocampus to detect mesial temporal sclerosis.", "Pituitary imaging uses small-FOV, thin (about 3 mm or less) sagittal and coronal T1, often with dynamic coronal post-contrast imaging; a microadenoma enhances more slowly than normal gland and appears dark early.", "IAC exams pair thin 3D heavily T2-weighted SSFP (CISS/FIESTA) with post-contrast fat-suppressed T1 to find vestibular schwannomas.", "Spine exams use sagittal T1, T2, and STIR plus axial T2. In the post-operative lumbar spine, gadolinium separates enhancing epidural scar from a non-enhancing recurrent disc.", "Liver and adrenal imaging use in-phase/opposed-phase GRE (signal loss on opposed-phase indicates intracellular fat) and multiphase dynamic contrast (arterial, portal venous, delayed); gadoxetate adds a hepatobiliary phase about 20 minutes after injection.", "MRCP uses heavily T2-weighted (very long TE) imaging so static fluid in the bile and pancreatic ducts is bright; fasting about 4 hours reduces bowel fluid and distends the gallbladder, and MIP reconstructions display the ducts.", "Prostate mpMRI combines high-resolution T2W, DWI with a high b-value (at least 1,400 s/mm²) and ADC, and dynamic contrast enhancement; female pelvis exams rely on T2W to show uterine zonal anatomy, often with an antiperistaltic agent.", "Breast MRI is done prone in a dedicated breast coil with dynamic fat-suppressed T1 before and after contrast plus subtraction; premenopausal patients are ideally scheduled in days 7–14 of the cycle.", "Cardiac MRI uses ECG gating (triggered on the R wave), SSFP cine for function, and late gadolinium enhancement about 10–20 minutes after injection, using an inversion time that nulls normal myocardium.", "MSK: angle knee sagittals parallel to the ACL; prescribe shoulder oblique coronals parallel to the supraspinatus tendon with the arm neutral or slightly externally rotated; use PD fat-suppressed sequences for cartilage and menisci; MR arthrography uses dilute intra-articular gadolinium with fat-suppressed T1; watch for the magic-angle effect (tendons at about 55° to B0 on short-TE images)." ], "vocabulary": [ { "term": "Dawson's fingers", "definition": "Ovoid MS plaques oriented perpendicular to the lateral ventricles, best seen on sagittal FLAIR." }, { "term": "Mesial temporal sclerosis", "definition": "Hippocampal scarring and atrophy, a common cause of temporal lobe epilepsy." }, { "term": "Microadenoma", "definition": "A pituitary adenoma smaller than 10 mm, often seen on dynamic contrast imaging as slowly enhancing." }, { "term": "Vestibular schwannoma", "definition": "A benign nerve-sheath tumor of the vestibulocochlear nerve in the internal auditory canal (acoustic neuroma)." }, { "term": "CISS / FIESTA", "definition": "Vendor names for 3D balanced SSFP sequences that give very thin, bright-fluid images of cranial nerves and IACs." }, { "term": "Opposed-phase imaging", "definition": "GRE imaging at a TE when fat and water signals cancel, showing signal loss in voxels containing both." }, { "term": "Hepatobiliary phase", "definition": "Delayed imaging after gadoxetate, when normal liver cells take up the agent and excrete it into the bile." }, { "term": "MRCP", "definition": "Magnetic resonance cholangiopancreatography; heavily T2-weighted imaging of the bile and pancreatic ducts." }, { "term": "Multiparametric MRI (mpMRI)", "definition": "A prostate exam combining T2W, DWI/ADC, and dynamic contrast enhancement." }, { "term": "Late gadolinium enhancement", "definition": "Delayed post-contrast inversion-recovery imaging that shows myocardial scar or fibrosis as bright." }, { "term": "ECG gating", "definition": "Synchronizing acquisition to the cardiac cycle, typically triggered by the R wave." }, { "term": "Respiratory triggering", "definition": "Acquiring data during a set phase of breathing, tracked with bellows or a navigator echo." }, { "term": "Magic angle effect", "definition": "Artificially high tendon signal on short-TE images when fibers lie about 55° to B0." }, { "term": "MR arthrography", "definition": "Imaging after intra-articular injection of dilute gadolinium (direct) or after IV contrast (indirect)." }, { "term": "ABER position", "definition": "Abduction and external rotation of the arm, used in shoulder arthrography to stress the anteroinferior labrum." }, { "term": "Bolus chase (moving table)", "definition": "A multistation contrast-enhanced MRA technique that follows the contrast bolus from the aorta down the legs." }, { "term": "MR enterography", "definition": "Small-bowel imaging after oral distending contrast, often with an antiperistaltic agent." }, { "term": "Dynamic contrast enhancement (DCE)", "definition": "Rapid repeated imaging during and after a contrast bolus to evaluate enhancement over time." } ], "quiz": [ { "q": "Which sequence and plane best show MS plaques oriented perpendicular to the lateral ventricles?", "options": [ "Axial T1 without contrast", "Coronal GRE", "Sagittal FLAIR", "Axial DWI" ], "answer_index": 2, "explanation": "Sagittal FLAIR suppresses CSF and displays the callososeptal and periventricular lesions known as Dawson's fingers." }, { "q": "For a seizure protocol, how are coronal T2/FLAIR slices oriented?", "options": [ "Perpendicular to the long axis of the hippocampus", "Parallel to the long axis of the hippocampus", "Parallel to the hard palate", "Perpendicular to the corpus callosum" ], "answer_index": 0, "explanation": "Oblique coronal slices perpendicular to the hippocampal axis show its internal structure and symmetry best for mesial temporal sclerosis." }, { "q": "On early dynamic post-contrast coronal images, how does a pituitary microadenoma usually appear compared with normal gland?", "options": [ "Hyperintense, because it enhances faster", "Isointense on every phase", "Signal void from calcification", "Hypointense, because it enhances more slowly" ], "answer_index": 3, "explanation": "Normal pituitary enhances rapidly, so a slower-enhancing microadenoma stands out as a dark focus on early images." }, { "q": "Which sequences are central to an IAC exam for suspected vestibular schwannoma?", "options": [ "Thick-slice axial FLAIR only", "Thin 3D heavily T2-weighted SSFP and post-contrast fat-suppressed T1", "Sagittal STIR of the cervical spine", "Whole-brain DWI only" ], "answer_index": 1, "explanation": "High-resolution T2 shows nerves outlined by CSF, and post-contrast T1 shows the enhancing tumor in the canal." }, { "q": "What is the main purpose of MRCP's very long TE?", "options": [ "To brighten fat for anatomic reference", "To make static fluid in the ducts bright while suppressing background tissue", "To null CSF signal", "To shorten the breath-hold" ], "answer_index": 1, "explanation": "Only fluids with very long T2 keep signal at long TE, so bile and pancreatic ducts stand out against a dark background." }, { "q": "An adrenal mass loses signal on opposed-phase compared with in-phase GRE images. What does this suggest?", "options": [ "A hemorrhagic metastasis", "A calcified granuloma", "A pheochromocytoma with flow voids", "A lipid-rich adenoma" ], "answer_index": 3, "explanation": "Signal drop on opposed-phase indicates intracellular fat and water in the same voxel, typical of benign lipid-rich adenomas." }, { "q": "After gadoxetate (a hepatobiliary agent), when is the hepatobiliary phase typically acquired?", "options": [ "About 20 minutes after injection", "About 20 seconds after injection", "About 70 seconds after injection", "24 hours after injection" ], "answer_index": 0, "explanation": "Hepatocytes take up gadoxetate over time, so the hepatobiliary phase is usually acquired around 20 minutes post-injection." }, { "q": "How is the oblique coronal plane prescribed for a shoulder MRI?", "options": [ "Perpendicular to the supraspinatus tendon", "Parallel to the humeral shaft on a sagittal image", "Parallel to the supraspinatus tendon on an axial image", "Parallel to the floor of the room" ], "answer_index": 2, "explanation": "Oblique coronals run along the supraspinatus tendon; oblique sagittals are perpendicular to it (parallel to the glenoid face)." }, { "q": "A normal tendon looks bright on a short-TE sequence but dark on T2W. It lies about 55° to B0. What is this?", "options": [ "Chemical shift artifact", "Gibbs truncation", "Zipper artifact", "Magic angle effect" ], "answer_index": 3, "explanation": "Tendon signal rises on short-TE images at about 55° to the main field; it disappears on long-TE sequences." }, { "q": "Which technique demonstrates myocardial scar on cardiac MRI?", "options": [ "Non-contrast SSFP cine only", "Inversion-recovery imaging about 10–20 minutes after gadolinium, with TI set to null normal myocardium", "Phase-contrast velocity mapping", "Time-of-flight angiography" ], "answer_index": 1, "explanation": "Gadolinium lingers in scar, which appears bright against nulled normal myocardium on late gadolinium enhancement images." }, { "q": "Why is gadolinium given for a post-operative lumbar spine exam?", "options": [ "To show the conus medullaris more clearly", "To reduce CSF flow artifact", "To differentiate enhancing epidural scar from non-enhancing recurrent disc", "To measure vertebral bone density" ], "answer_index": 2, "explanation": "Granulation and scar tissue enhance, while recurrent disc material does not enhance centrally, which guides surgical planning." }, { "q": "How is a patient typically positioned for breast MRI?", "options": [ "Prone, with the breasts hanging into a dedicated breast coil", "Supine with arms at the sides in a body coil", "Left lateral decubitus in a head coil", "Seated upright" ], "answer_index": 0, "explanation": "Prone positioning in a dedicated coil reduces breathing motion and lets the breasts fall into the coil wells." } ], "bank": [ { "q": "Which sequence is most sensitive for detecting cerebral microbleeds?", "options": [ "Susceptibility-weighted imaging (SWI)", "T1-weighted spin echo", "STIR", "FLAIR" ], "answer_index": 0, "explanation": "Blood products such as hemosiderin cause strong susceptibility effects, which SWI exaggerates for maximum sensitivity.", "subcategory": "Neurological" }, { "q": "Which sequence best shows optic nerve enhancement in suspected optic neuritis?", "options": [ "Axial DWI of the brain only", "Axial non-contrast FLAIR of the brain", "Coronal fat-suppressed post-contrast T1 through the orbits", "Sagittal T2 of the cervical spine" ], "answer_index": 2, "explanation": "Fat suppression removes bright orbital fat so optic nerve enhancement can be seen on coronal post-contrast images.", "subcategory": "Neurological" }, { "q": "How is dynamic susceptibility contrast (DSC) perfusion of the brain performed?", "options": [ "Arterial spin labeling without contrast", "Phase-contrast imaging of the carotids", "Rapid T2*-weighted EPI during a fast gadolinium bolus (about 4-5 mL/s)", "Delayed T1 imaging 10 minutes after a slow drip injection" ], "answer_index": 2, "explanation": "DSC tracks the signal drop as the gadolinium bolus passes, from which maps such as relative cerebral blood volume are calculated.", "subcategory": "Neurological" }, { "q": "Which perfusion technique needs no contrast agent?", "options": [ "Dynamic susceptibility contrast (DSC)", "Arterial spin labeling (ASL)", "Dynamic contrast-enhanced (DCE) T1", "Contrast-enhanced MRA" ], "answer_index": 1, "explanation": "ASL magnetically labels inflowing arterial blood water as an endogenous tracer.", "subcategory": "Neurological" }, { "q": "What is the minimum number of diffusion-gradient directions needed to calculate a diffusion tensor for tractography?", "options": [ "6", "4", "1", "3" ], "answer_index": 0, "explanation": "The tensor has six independent elements, so at least six non-collinear directions (plus a b=0 image) are needed.", "subcategory": "Neurological" }, { "q": "Functional MRI using the BOLD technique is based on which principle?", "options": [ "Changes in the ratio of oxyhemoglobin to paramagnetic deoxyhemoglobin with brain activity", "Increased proton density in active neurons", "Lactate production in active cortex", "Gadolinium leakage into active cortex" ], "answer_index": 0, "explanation": "Active brain gets more oxygenated blood than it uses, reducing deoxyhemoglobin and increasing T2* signal.", "subcategory": "Neurological" }, { "q": "For 2D time-of-flight MR venography of the dural sinuses, where should the saturation band go?", "options": [ "Inferior to the slices, to suppress arterial inflow", "Superior to the slices, to suppress venous inflow", "No saturation band is ever used", "Over the orbits" ], "answer_index": 0, "explanation": "Arterial blood enters the head from below, so an inferior saturation band suppresses it and leaves venous flow visible.", "subcategory": "Neurological" }, { "q": "In brain proton spectroscopy at TE 144 ms, how does lactate appear?", "options": [ "As an upright singlet at 3.2 ppm", "As an upright peak at 3.0 ppm", "As an inverted doublet at about 1.3 ppm", "As an inverted peak at 2.0 ppm" ], "answer_index": 2, "explanation": "J-coupling makes the lactate doublet invert at TE 135-144 ms, separating it from lipid.", "subcategory": "Neurological" }, { "q": "Which technique evaluates CSF flow at the foramen magnum or cerebral aqueduct, such as in Chiari I malformation?", "options": [ "Diffusion tensor imaging", "Arterial spin labeling", "Cardiac-gated phase-contrast cine imaging", "Magnetization transfer imaging" ], "answer_index": 2, "explanation": "Phase-contrast cine encodes velocity across the cardiac cycle, showing whether CSF pulsation is normal or obstructed.", "subcategory": "Neurological" }, { "q": "On a stroke MRI, a lesion is clearly bright on DWI but not yet visible on FLAIR. What does this DWI-FLAIR mismatch suggest?", "options": [ "The finding is a T2 shine-through artifact", "The lesion is a chronic gliotic scar", "The infarct is likely less than about 4.5 hours old", "The infarct is more than 1 week old" ], "answer_index": 2, "explanation": "FLAIR changes appear hours after onset, so a DWI-positive, FLAIR-negative lesion suggests an early infarct, which can guide treatment when onset time is unknown.", "subcategory": "Neurological" }, { "q": "On a multiple sclerosis follow-up exam, which finding indicates an actively demyelinating lesion?", "options": [ "Bright signal on SWI", "Dark signal on T1 ('black hole')", "Enhancement on post-contrast T1-weighted images", "Bright signal on FLAIR without enhancement" ], "answer_index": 2, "explanation": "Enhancement reflects blood-brain barrier breakdown during active inflammation; non-enhancing FLAIR lesions may be old.", "subcategory": "Neurological" }, { "q": "On a T2-weighted brain scan of a full-term newborn, how does white matter look compared with gray matter?", "options": [ "Brighter, because the white matter is largely unmyelinated and high in water", "Darker, as in adults", "Dark because of iron deposition", "Identical to gray matter" ], "answer_index": 0, "explanation": "Before myelination, white matter has high water content, reversing adult gray-white contrast on T2.", "subcategory": "Neurological" }, { "q": "At approximately which vertebral level does the conus medullaris normally end in adults?", "options": [ "S1", "L1-L2", "L3-L4", "T10-T11" ], "answer_index": 1, "explanation": "A conus ending below about L2-L3 is low-lying and suggests a tethered cord.", "subcategory": "Neurological" }, { "q": "Which sequences best support a diagnosis of vertebral discitis-osteomyelitis?", "options": [ "Axial GRE only", "Sagittal T1 only", "Sagittal STIR (or fat-suppressed T2) and fat-suppressed post-contrast T1", "DWI of the brain" ], "answer_index": 2, "explanation": "Fluid-sensitive images show marrow and disc edema, and post-contrast fat-suppressed images show enhancement and abscesses.", "subcategory": "Neurological" }, { "q": "How is the temporomandibular joint typically imaged to assess disc position?", "options": [ "Oblique sagittal PD images in closed-mouth and open-mouth positions", "Coronal DWI with the mouth open", "Sagittal STIR of the cervical spine", "Axial T1 with the mouth closed only" ], "answer_index": 0, "explanation": "Comparing closed and open positions shows whether the disc is displaced and whether it reduces on opening.", "subcategory": "Neurological" }, { "q": "For a patient with cervical radiculopathy, which axial sequence is commonly used to evaluate the neural foramina?", "options": [ "Axial STIR of the brain", "Axial post-contrast T1 only", "Axial T2*-weighted GRE or 3D T2 through the disc levels", "Axial DWI only" ], "answer_index": 2, "explanation": "GRE or 3D T2 axial images give good contrast between CSF, cord, disc, and bony foramina in the cervical spine.", "subcategory": "Neurological" }, { "q": "Why is a large volume of neutral or biphasic oral contrast given for MR enterography?", "options": [ "To shorten the T1 of the liver", "To reduce SAR", "To replace the need for IV gadolinium", "To distend the small bowel so wall thickening and enhancement can be assessed" ], "answer_index": 3, "explanation": "Collapsed bowel can mimic wall thickening; distension with an agent such as mannitol or sorbitol solution allows accurate assessment.", "subcategory": "Body" }, { "q": "On breast DCE-MRI, a lesion shows rapid initial enhancement followed by signal decline (washout). Which kinetic curve is this?", "options": [ "Type 0, no enhancement", "Type III, most suspicious for malignancy", "Type II (plateau), always benign", "Type I (persistent), usually benign" ], "answer_index": 1, "explanation": "A washout curve (Type III) is the pattern most associated with malignancy.", "subcategory": "Body" }, { "q": "To evaluate silicone breast implant integrity, which acquisition is most specific?", "options": [ "A silicone-selective sequence that suppresses both fat and water", "A post-contrast fat-suppressed T1 only", "A water-suppressed DWI", "A T1-weighted image without fat suppression" ], "answer_index": 0, "explanation": "Silicone-only images make implant contents bright, revealing intracapsular rupture (linguine sign) and free silicone.", "subcategory": "Body" }, { "q": "Which technique quantifies myocardial or hepatic iron overload?", "options": [ "Arterial spin labeling", "Magnetization transfer imaging", "Diffusion-weighted imaging", "Multi-echo gradient-echo T2* measurement" ], "answer_index": 3, "explanation": "Iron shortens T2*, so measuring signal decay across multiple echoes estimates tissue iron.", "subcategory": "Body" }, { "q": "Which pattern is typical of a liver hemangioma on MRI?", "options": [ "Uniform hepatobiliary-phase uptake", "Dark on T2 with no enhancement", "Very bright on heavily T2-weighted images with peripheral nodular discontinuous enhancement that fills in", "Arterial enhancement with washout and a capsule" ], "answer_index": 2, "explanation": "A 'light bulb' T2 signal with progressive peripheral nodular fill-in is the classic hemangioma appearance.", "subcategory": "Body" }, { "q": "Under PI-RADS v2.1, which sequence is dominant for scoring a peripheral-zone lesion?", "options": [ "T2-weighted imaging", "Diffusion-weighted imaging (with the ADC map)", "T1-weighted imaging", "Dynamic contrast-enhanced imaging" ], "answer_index": 1, "explanation": "DWI drives the peripheral zone score; T2W is dominant for the transition zone.", "subcategory": "Body" }, { "q": "For MRI of a perianal fistula, how are high-resolution T2 oblique axial images prescribed?", "options": [ "Parallel to the sacrum", "Parallel to the anal canal", "Perpendicular to the femoral heads", "Perpendicular to the long axis of the anal canal" ], "answer_index": 3, "explanation": "Slices perpendicular to the anal canal show the sphincter complex and the fistula's relationship to it.", "subcategory": "Body" }, { "q": "What is the purpose of giving secretin during MRCP?", "options": [ "To darken the bowel signal", "To reduce peristalsis", "To shorten T1 of the bile", "To stimulate pancreatic fluid secretion, improving visualization of the pancreatic duct" ], "answer_index": 3, "explanation": "Secretin distends the pancreatic duct and allows assessment of exocrine function.", "subcategory": "Body" }, { "q": "Which sequence is typically used for contrast-enhanced MRA of the renal arteries?", "options": [ "Fast spin-echo T2", "Breath-hold 3D T1-weighted spoiled gradient echo timed to the arterial bolus", "2D FLAIR", "Diffusion-weighted EPI" ], "answer_index": 1, "explanation": "A fast 3D spoiled GRE captures the T1-shortening of gadolinium during first arterial passage.", "subcategory": "Body" }, { "q": "For direct MR arthrography, gadolinium is typically diluted to about:", "options": [ "1:200 (roughly 2 mmol/L)", "1:20", "Undiluted", "1:2" ], "answer_index": 0, "explanation": "A dilute concentration gives optimal T1 shortening; concentrations too high cause signal loss from T2* effects.", "subcategory": "Musculoskeletal" }, { "q": "Which plane best shows the full length of the Achilles tendon?", "options": [ "Axial", "Coronal", "Sagittal", "Oblique axial to the subtalar joint" ], "answer_index": 2, "explanation": "The Achilles runs longitudinally, so sagittal images show it from the muscle to the calcaneal insertion.", "subcategory": "Musculoskeletal" }, { "q": "A patient on long-term steroids has hip pain. Which protocol best screens both hips for avascular necrosis?", "options": [ "MR arthrogram of the painful hip only", "Sagittal DWI of the lumbar spine", "Large-FOV coronal T1 and STIR covering both hips", "Small-FOV axial PD of the painful hip only" ], "answer_index": 2, "explanation": "AVN is often bilateral; coronal T1 and STIR of both hips detect the early marrow changes.", "subcategory": "Musculoskeletal" }, { "q": "Which sequence is best for detecting bone marrow replacement by tumor?", "options": [ "FLAIR", "T1-weighted spin echo without fat suppression", "Post-contrast fat-suppressed T1 only", "Gradient-echo T2*" ], "answer_index": 1, "explanation": "Normal fatty marrow is bright on T1; marrow replaced by tumor becomes dark, often darker than muscle or disc.", "subcategory": "Musculoskeletal" }, { "q": "A patient has wrist pain after a fall and normal radiographs. On MRI, a dark line on T1 crosses the scaphoid waist with surrounding marrow edema on STIR. What does this indicate?", "options": [ "Normal marrow variant", "TFCC tear", "Occult scaphoid fracture", "Kienbock disease" ], "answer_index": 2, "explanation": "MRI detects fractures hidden on radiographs: a T1 dark fracture line with edema on fluid-sensitive images.", "subcategory": "Musculoskeletal" }, { "q": "On a sagittal knee image, a band of tissue lies parallel to and just beneath the PCL. Which injury does this sign suggest?", "options": [ "A quadriceps tendon tear", "A bucket-handle tear of the medial meniscus", "A Baker cyst", "A complete ACL tear" ], "answer_index": 1, "explanation": "The 'double PCL' sign is a displaced fragment of a bucket-handle meniscal tear flipped into the intercondylar notch.", "subcategory": "Musculoskeletal" }, { "q": "During shoulder MR arthrography, why is the ABER (abduction and external rotation) position added?", "options": [ "To tension the anteroinferior labrum and undersurface of the cuff, revealing subtle tears", "To bring the shoulder to isocenter for fat suppression", "To show the acromioclavicular joint", "To reduce SAR" ], "answer_index": 0, "explanation": "ABER stresses the anteroinferior labroligamentous complex and articular-side cuff fibers, increasing tear detection.", "subcategory": "Musculoskeletal" }, { "q": "In a skier's thumb injury, MRI shows the torn ulnar collateral ligament displaced superficial to the adductor aponeurosis. What is this?", "options": [ "A Bankart lesion", "A Stener lesion", "A Segond fracture", "A Hill-Sachs lesion" ], "answer_index": 1, "explanation": "A Stener lesion blocks healing because the aponeurosis is trapped between the ligament and its insertion, so surgery is often needed.", "subcategory": "Musculoskeletal" }, { "q": "Which sequence best shows a muscle strain as feathery high signal?", "options": [ "Time-of-flight MRA", "T1-weighted images without fat suppression", "Gradient-echo T2*", "Fat-suppressed T2-weighted or STIR images" ], "answer_index": 3, "explanation": "Edema and hemorrhage from strain are most visible on fluid-sensitive, fat-suppressed sequences.", "subcategory": "Musculoskeletal" }, { "q": "Why is a skin marker (such as a vitamin E capsule) placed over a palpable soft-tissue lump before imaging?", "options": [ "To serve as a phantom for SNR measurements", "To show exactly where the area of clinical concern is on the images", "To reduce chemical shift artifact", "To trigger the scan from respiration" ], "answer_index": 1, "explanation": "The marker is bright on MRI and confirms that the imaged area matches the palpable abnormality.", "subcategory": "Musculoskeletal" }, { "q": "After a lateral patellar dislocation that has reduced, which bone bruise pattern is classic on knee MRI?", "options": [ "Medial patellar facet and lateral femoral condyle", "Femoral trochlea and fibular head", "Medial femoral condyle and medial tibial plateau", "Posterior tibial plateau only" ], "answer_index": 0, "explanation": "When the patella dislocates laterally and then snaps back, the medial patella strikes the lateral femoral condyle.", "subcategory": "Musculoskeletal" }, { "q": "On brain MRI, a hematoma is bright on both T1- and T2-weighted images. Which stage is most likely?", "options": [ "Late subacute (extracellular methemoglobin)", "Chronic (hemosiderin)", "Acute (deoxyhemoglobin)", "Hyperacute (oxyhemoglobin)" ], "answer_index": 0, "explanation": "Extracellular methemoglobin in the late subacute stage shortens T1 and is no longer compartmentalized, so it is bright on both T1 and T2.", "subcategory": "Neurological" }, { "q": "A cerebellopontine angle mass follows CSF signal on T1 and T2. Which finding favors an epidermoid over an arachnoid cyst?", "options": [ "Complete suppression on FLAIR", "No enhancement after contrast", "Restricted diffusion, with high signal on DWI", "Dark signal on DWI, like CSF" ], "answer_index": 2, "explanation": "Epidermoids restrict diffusion and are bright on DWI, while arachnoid cysts follow CSF on all sequences, including DWI and FLAIR.", "subcategory": "Neurological" }, { "q": "On sagittal non-contrast T1 images of the sella, what causes the normal bright spot in the posterior pituitary?", "options": [ "Fat within the sella turcica", "Small hemorrhages from the pituitary stalk", "Calcification of the posterior lobe", "Vasopressin-containing neurosecretory granules" ], "answer_index": 3, "explanation": "The posterior pituitary bright spot reflects stored vasopressin granules; its absence can be seen in central diabetes insipidus.", "subcategory": "Neurological" }, { "q": "A patient with a known primary brain tumor has new back pain. Which addition best looks for drop metastases?", "options": [ "Coronal STIR of the sacroiliac joints", "Sagittal post-contrast T1 of the entire spine", "Axial T2 GRE through the cervical spine only", "Sagittal non-contrast T1 of the lumbar spine only" ], "answer_index": 1, "explanation": "Leptomeningeal (drop) metastases are best seen as enhancement along the cord and nerve roots on post-contrast T1 covering the whole spine.", "subcategory": "Neurological" }, { "q": "Which sagittal sequence is commonly added to improve detection of multiple sclerosis lesions in the cervical spinal cord?", "options": [ "STIR (or proton density) in addition to T2", "Non-contrast T1 spin echo only", "FLAIR alone, as in the brain", "T2* GRE with long TE only" ], "answer_index": 0, "explanation": "Sagittal FLAIR is unreliable in the cord; STIR or PD images added to T2 increase detection of cord MS lesions.", "subcategory": "Neurological" }, { "q": "For trigeminal neuralgia, which sequence combination best shows a vessel compressing the nerve root entry zone?", "options": [ "Thin 3D heavily T2-weighted images plus 3D time-of-flight MRA", "Thick-slice coronal T1 plus sagittal STIR", "Axial SWI plus single-voxel spectroscopy", "Axial FLAIR plus axial diffusion-weighted imaging" ], "answer_index": 0, "explanation": "High-resolution 3D T2 shows the nerve against bright CSF, and 3D TOF identifies the offending artery at the root entry zone.", "subcategory": "Neurological" }, { "q": "A ring-enhancing brain lesion shows markedly restricted diffusion in its center. This finding most favors:", "options": [ "A resolving hematoma", "A necrotic glioblastoma", "A pyogenic abscess", "A cystic metastasis" ], "answer_index": 2, "explanation": "Thick pus in an abscess restricts diffusion centrally, whereas necrotic tumor cores usually show facilitated diffusion.", "subcategory": "Neurological" }, { "q": "A patient with rapidly progressing dementia has cortical ribbon-like high signal on DWI along with signal in the caudate and putamen. This pattern suggests:", "options": [ "Multiple sclerosis", "Normal pressure hydrocephalus", "Alzheimer disease", "Creutzfeldt-Jakob disease" ], "answer_index": 3, "explanation": "Cortical ribboning and basal ganglia restricted diffusion are characteristic MRI findings of Creutzfeldt-Jakob disease.", "subcategory": "Neurological" }, { "q": "A febrile, confused patient has asymmetric T2/FLAIR high signal in the medial temporal lobe and insula. Which diagnosis is most likely?", "options": [ "Central pontine myelinolysis", "Hypertensive encephalopathy", "Acute lacunar infarct", "Herpes simplex encephalitis" ], "answer_index": 3, "explanation": "Herpes simplex encephalitis classically involves the medial temporal lobes, insula, and inferior frontal lobes, often asymmetrically.", "subcategory": "Neurological" }, { "q": "On post-contrast images, a triangular filling defect is outlined by enhancing walls of the superior sagittal sinus. This 'empty delta' sign indicates:", "options": [ "Dural venous sinus thrombosis", "A normal flow void", "A subdural hematoma", "An arachnoid granulation" ], "answer_index": 0, "explanation": "The empty delta sign is a non-enhancing clot surrounded by the enhancing dural walls of the sinus, signaling venous sinus thrombosis.", "subcategory": "Neurological" }, { "q": "Vertebral endplate marrow next to a degenerated disc is dark on T1 and bright on T2. Which Modic type is this?", "options": [ "Type 2 (fatty replacement)", "Type 0 (normal marrow)", "Type 3 (sclerosis)", "Type 1 (edema and inflammation)" ], "answer_index": 3, "explanation": "Modic type 1 changes reflect marrow edema (low T1, high T2); type 2 is fatty (high T1); type 3 is sclerotic (low on both).", "subcategory": "Neurological" }, { "q": "On axial lumbar images, disc material beyond the disc space is wider than its base at the parent disc. This herniation is classified as:", "options": [ "An extrusion", "A diffuse bulge", "An annular fissure", "A protrusion" ], "answer_index": 0, "explanation": "In an extrusion, the displaced disc material is wider than its base in at least one plane; in a protrusion, the base is widest.", "subcategory": "Neurological" }, { "q": "How are axial slices usually prescribed through the lumbar intervertebral discs?", "options": [ "Parallel to the posterior vertebral body line", "Angled parallel to the sacral promontory for all levels", "Angled parallel to each disc space on the sagittal localizer", "Perpendicular to the table regardless of disc angle" ], "answer_index": 2, "explanation": "Angling axial slices parallel to each disc avoids partial volume averaging and shows the disc, canal, and foramina in true cross-section.", "subcategory": "Neurological" }, { "q": "On a sagittal brain or cervical spine image, Chiari I malformation is generally diagnosed when the cerebellar tonsils extend below the foramen magnum by at least:", "options": [ "1 mm", "25 mm", "5 mm", "15 mm" ], "answer_index": 2, "explanation": "Tonsillar descent of 5 mm or more below the basion-opisthion line is the usual threshold for Chiari I malformation.", "subcategory": "Neurological" }, { "q": "A 10-day-old infarct is bright on DWI, but the ADC map shows near-normal values. What best explains the bright DWI signal?", "options": [ "Magnetic susceptibility artifact", "Hyperacute cytotoxic edema", "Hemorrhagic conversion only", "T2 shine-through" ], "answer_index": 3, "explanation": "As ADC pseudonormalizes, persisting long-T2 signal can still make the lesion bright on DWI; the ADC map separates shine-through from true restriction.", "subcategory": "Neurological" }, { "q": "Months after radiation for a high-grade glioma, a new enhancing lesion appears. Which perfusion finding favors recurrent tumor over radiation necrosis?", "options": [ "Elevated relative cerebral blood volume (rCBV)", "Low choline on MR spectroscopy", "No signal change during the contrast bolus", "Decreased relative cerebral blood volume" ], "answer_index": 0, "explanation": "Recurrent tumor has neoangiogenesis with high rCBV, whereas radiation necrosis typically shows low rCBV.", "subcategory": "Neurological" }, { "q": "In brain proton MR spectroscopy, an elevated choline peak at about 3.2 ppm most often reflects:", "options": [ "Lipid released by necrosis", "Increased cell membrane turnover, as in tumor", "Anaerobic metabolism from ischemia", "Normal neuronal density" ], "answer_index": 1, "explanation": "Choline reflects membrane synthesis and breakdown; it rises in proliferating tumors, often with a falling NAA.", "subcategory": "Neurological" }, { "q": "For routine axial brain imaging, slices are commonly aligned with which reference line on the sagittal localizer?", "options": [ "The line parallel to the hard palate", "The line from nasion to the external occipital protuberance", "The line along the clivus", "The anterior commissure-posterior commissure (AC-PC) line" ], "answer_index": 3, "explanation": "Aligning axial slices to the AC-PC line gives a reproducible orientation that eases follow-up comparison.", "subcategory": "Neurological" }, { "q": "A young patient with neck pain and Horner syndrome is evaluated for carotid dissection. Which sequence best shows the intramural hematoma?", "options": [ "Sagittal STIR of the cervical spine", "Axial non-fat-suppressed T2 FSE", "Axial fat-suppressed T1 through the neck", "Coronal 2D TOF MRA" ], "answer_index": 2, "explanation": "Subacute intramural hematoma is a bright crescent on T1, and fat suppression separates it from surrounding fat.", "subcategory": "Neurological" }, { "q": "A patient with rapidly ascending weakness after a viral illness has smooth enhancement of the cauda equina nerve roots on post-contrast T1. This suggests:", "options": [ "Lumbar spinal stenosis", "Spinal cord infarction", "Tethered spinal cord", "Guillain-Barré syndrome" ], "answer_index": 3, "explanation": "Smooth enhancement of the cauda equina nerve roots, often favoring the ventral roots, supports Guillain-Barré syndrome.", "subcategory": "Neurological" }, { "q": "After a high-speed car crash, a cervical spine MRI is ordered to check for ligament injury. Which sequence is most sensitive?", "options": [ "Sagittal STIR", "Sagittal non-contrast T1", "Sagittal post-contrast T1", "Axial T2* GRE" ], "answer_index": 0, "explanation": "STIR shows edema in ligaments, discs, and prevertebral soft tissues with strong fat suppression, which makes subtle ligament injury easier to see.", "subcategory": "Neurological" }, { "q": "In thyroid eye disease, which extraocular muscles are most commonly enlarged on coronal orbital images?", "options": [ "Lateral and superior rectus", "Inferior oblique and superior rectus", "Superior oblique and lateral rectus", "Inferior and medial rectus" ], "answer_index": 3, "explanation": "Thyroid eye disease usually enlarges the inferior and medial recti first, typically sparing the tendon insertions.", "subcategory": "Neurological" }, { "q": "On coronal images in a patient with temporal lobe epilepsy, which findings indicate mesial temporal (hippocampal) sclerosis?", "options": [ "Hippocampal volume loss with increased T2/FLAIR signal", "Restricted diffusion in the occipital cortex", "Hippocampal enlargement with enhancement", "Bright T1 signal in the globus pallidus" ], "answer_index": 0, "explanation": "Mesial temporal sclerosis shows atrophy, increased T2/FLAIR signal, and loss of internal architecture in the affected hippocampus.", "subcategory": "Neurological" }, { "q": "When placing a single-voxel MR spectroscopy box in the brain, why should the scalp and skull be avoided?", "options": [ "Scalp tissue raises SAR above the limit", "Bone causes the water peak to disappear", "Placing it there lengthens scan time", "Lipid from scalp fat and marrow can contaminate the spectrum" ], "answer_index": 3, "explanation": "Large lipid signals from outside the brain can overlap metabolite peaks, so voxels are kept within brain tissue, often with saturation bands.", "subcategory": "Neurological" }, { "q": "Which b-value is most commonly used for routine diffusion-weighted brain imaging in suspected stroke?", "options": [ "b = 50 s/mm²", "b = 300 s/mm²", "b = 1,000 s/mm²", "b = 3,000 s/mm²" ], "answer_index": 2, "explanation": "Routine brain DWI uses a b-value of about 1,000 s/mm², along with b = 0 images, to calculate the ADC map.", "subcategory": "Neurological" }, { "q": "Which technique provides a quantitative measure of liver fat?", "options": [ "Arterial-phase dynamic contrast imaging", "Proton density fat fraction (PDFF) from multi-echo chemical-shift imaging", "Single-shot T2 with spectral fat saturation", "Diffusion-weighted imaging at a high b-value" ], "answer_index": 1, "explanation": "Multi-echo Dixon-based PDFF corrects for T2* and other confounders to give a reliable percentage of liver fat.", "subcategory": "Body" }, { "q": "In a cirrhotic liver, a 2.5 cm observation shows arterial phase hyperenhancement, washout on portal venous images, and an enhancing capsule. This is most consistent with:", "options": [ "Simple hepatic cyst", "Typical hemangioma", "Hepatocellular carcinoma", "Focal nodular hyperplasia" ], "answer_index": 2, "explanation": "Arterial hyperenhancement with washout and capsule in a cirrhotic liver are major LI-RADS features of hepatocellular carcinoma.", "subcategory": "Body" }, { "q": "On a multiphase liver exam, the portal venous phase is typically acquired about how long after the start of gadolinium injection?", "options": [ "10-15 seconds", "60-70 seconds", "20 minutes", "3-5 minutes" ], "answer_index": 1, "explanation": "The portal venous phase is usually acquired about 60-70 seconds after injection, following the late arterial phase.", "subcategory": "Body" }, { "q": "For local staging of rectal cancer, which sequence is the key acquisition for judging tumor depth and the distance to the mesorectal fascia?", "options": [ "Fat-suppressed T1 before contrast only", "Large-FOV coronal STIR through the pelvis", "High-resolution small-FOV T2 without fat suppression", "Single-shot FSE with a 40 cm FOV" ], "answer_index": 2, "explanation": "High-resolution T2 images angled to the tumor show the bowel wall layers, mesorectal fat, and mesorectal fascia, which drive staging and surgical planning.", "subcategory": "Body" }, { "q": "A patient had a prostate biopsy last week and is scheduled for multiparametric prostate MRI. What do PI-RADS recommendations suggest?", "options": [ "Delay 6 months, since biopsy changes last for years", "Scan right away, since hemorrhage improves lesion contrast", "Cancel the MRI, since a biopsy already gave the answer", "Consider delaying the MRI at least 6 weeks so biopsy hemorrhage can resolve" ], "answer_index": 3, "explanation": "Post-biopsy hemorrhage can obscure or mimic tumor, so PI-RADS suggests waiting at least 6 weeks when MRI follows biopsy.", "subcategory": "Body" }, { "q": "An ovarian cyst is very bright on T1 and fat-suppressed T1 and shows layering low signal ('shading') on T2. This suggests:", "options": [ "A simple follicular cyst", "An endometrioma", "A hydrosalpinx", "A mature cystic teratoma" ], "answer_index": 1, "explanation": "Repeated hemorrhage gives endometriomas high T1 signal that persists with fat suppression, plus T2 shading.", "subcategory": "Body" }, { "q": "How is the short-axis cine stack of the left ventricle prescribed?", "options": [ "Perpendicular to the aortic root, from the arch to the valve", "Parallel to the long axis of the left ventricle", "Parallel to the interventricular septum on an axial image", "Perpendicular to the long axis of the LV, from the mitral valve to the apex" ], "answer_index": 3, "explanation": "Short-axis slices are set perpendicular to the LV long axis on 2- and 4-chamber views, covering base to apex for volume measurements.", "subcategory": "Body" }, { "q": "A premenopausal woman is scheduled for an elective high-risk screening breast MRI. When is the exam ideally performed?", "options": [ "Timing does not matter for breast MRI", "During the last week of the menstrual cycle", "During the second week of the menstrual cycle (about days 7-14)", "During menstruation (days 1-3)" ], "answer_index": 2, "explanation": "Background parenchymal enhancement is lowest in the second week of the cycle, which reduces false-positive enhancement.", "subcategory": "Body" }, { "q": "A renal mass contains areas that lose signal on fat-suppressed images compared with matching non-suppressed images. This most suggests:", "options": [ "Renal oncocytoma", "Hemorrhagic renal cyst", "Clear cell renal cell carcinoma", "Angiomyolipoma with macroscopic fat" ], "answer_index": 3, "explanation": "Signal loss with frequency-selective fat suppression shows macroscopic fat, the hallmark of an angiomyolipoma.", "subcategory": "Body" }, { "q": "Why might a negative oral contrast agent, such as pineapple juice, be given before MRCP?", "options": [ "To stimulate pancreatic secretion like secretin does", "To darken fluid in the stomach and duodenum that overlaps the ducts", "To make the bile ducts brighter on T1 images", "To distend the small bowel for wall assessment" ], "answer_index": 1, "explanation": "Negative oral agents shorten T2 of gastric and duodenal fluid, removing overlapping bright signal on heavily T2-weighted MRCP images.", "subcategory": "Body" }, { "q": "Why are patients usually asked to fast for about 4 hours before MRCP?", "options": [ "To lower the risk of a gadolinium reaction", "To reduce bowel fluid and peristalsis, and to distend the gallbladder", "To shorten the T1 of bile in the ducts", "To lower the patient's SAR during scanning" ], "answer_index": 1, "explanation": "Fasting reduces overlapping gastrointestinal fluid and motion and keeps the gallbladder distended with bile.", "subcategory": "Body" }, { "q": "Which sequence is the workhorse of fetal MRI for showing anatomy despite fetal movement?", "options": [ "Long-TR conventional T2 spin echo", "Single-shot fast spin echo (T2 HASTE/SSFSE)", "Conventional spin-echo T1 with multiple NEX", "3D spoiled gradient echo with 8 averages" ], "answer_index": 1, "explanation": "Single-shot FSE collects each slice in under a second, freezing fetal motion while giving T2 contrast.", "subcategory": "Body" }, { "q": "On the hepatobiliary phase after gadoxetate, a liver lesion is iso- to hyperintense to the surrounding liver. Which lesion is most likely?", "options": [ "Focal nodular hyperplasia", "Liver metastasis", "Hepatocellular adenoma", "Hepatic cyst" ], "answer_index": 0, "explanation": "FNH contains functioning hepatocytes with disordered bile ducts, so it retains gadoxetate; most adenomas and metastases appear hypointense.", "subcategory": "Body" }, { "q": "On late gadolinium enhancement cardiac MRI, which pattern is more typical of myocarditis than of myocardial infarction?", "options": [ "Subepicardial or mid-wall enhancement", "Transmural enhancement following one coronary territory", "No enhancement in the area of abnormal motion", "Subendocardial enhancement in a coronary territory" ], "answer_index": 0, "explanation": "Infarcts begin at the subendocardium in a vascular territory, while myocarditis typically spares it, with subepicardial or mid-wall enhancement.", "subcategory": "Body" }, { "q": "During contrast-enhanced MR urography, why is a low dose of furosemide often given?", "options": [ "To suppress the signal from fat in the pelvis", "To reduce the risk of nephrogenic systemic fibrosis", "To improve urinary tract distension and spread the contrast evenly", "To slow down the kidneys' excretion of contrast" ], "answer_index": 2, "explanation": "Furosemide increases urine flow, distending the collecting systems and ureters and diluting gadolinium to avoid T2* signal loss.", "subcategory": "Body" }, { "q": "A patient with lateral elbow pain has thickening and high T2 signal at the lateral epicondyle. Which tendon is involved in this lateral epicondylitis?", "options": [ "The common flexor tendon", "The common extensor tendon", "The triceps tendon", "The distal biceps tendon" ], "answer_index": 1, "explanation": "Lateral epicondylitis (tennis elbow) involves the common extensor tendon origin, especially the extensor carpi radialis brevis, best seen on coronal images.", "subcategory": "Musculoskeletal" }, { "q": "A small avulsion fracture of the lateral tibial plateau (Segond fracture) is seen on knee imaging. Which injury is most strongly associated?", "options": [ "Posterior cruciate ligament tear", "Medial collateral ligament tear", "Quadriceps tendon rupture", "Anterior cruciate ligament tear" ], "answer_index": 3, "explanation": "A Segond fracture has a very high association with ACL tears and often with meniscal injury.", "subcategory": "Musculoskeletal" }, { "q": "A knee MRI shows bone bruises in the lateral femoral condyle and posterolateral tibial plateau. This pivot-shift pattern suggests a tear of the:", "options": [ "Anterior cruciate ligament", "Patellar tendon", "Posterior cruciate ligament", "Lateral collateral ligament" ], "answer_index": 0, "explanation": "The pivot-shift mechanism of ACL rupture impacts the lateral femoral condyle against the posterolateral tibial plateau.", "subcategory": "Musculoskeletal" }, { "q": "After an anterior shoulder dislocation, an impaction fracture of the posterolateral humeral head is seen. This is called a:", "options": [ "Hill-Sachs lesion", "Reverse Hill-Sachs lesion", "Bennett lesion", "Bankart lesion" ], "answer_index": 0, "explanation": "The posterolateral humeral head strikes the anteroinferior glenoid during anterior dislocation, producing a Hill-Sachs lesion.", "subcategory": "Musculoskeletal" }, { "q": "A SLAP tear involves which part of the shoulder?", "options": [ "The superior labrum at the long head biceps anchor", "The supraspinatus tendon insertion", "The anteroinferior labrum only", "The posterior capsule and teres minor" ], "answer_index": 0, "explanation": "SLAP stands for superior labrum anterior to posterior; these tears center on the biceps-labral anchor.", "subcategory": "Musculoskeletal" }, { "q": "For hip MR arthrography assessing cam-type femoroacetabular impingement, which plane is commonly added to measure the alpha angle?", "options": [ "Straight sagittal through the acetabular roof", "Coronal perpendicular to the femoral shaft", "Oblique axial parallel to the femoral neck", "Axial perpendicular to the sacrum" ], "answer_index": 2, "explanation": "Oblique axial (or radial) images along the femoral neck show the anterior head-neck junction, where the cam deformity and alpha angle are measured.", "subcategory": "Musculoskeletal" }, { "q": "Which ankle ligament is most commonly injured in an inversion sprain, and which plane shows it best?", "options": [ "Posterior talofibular ligament, on coronal images", "Anterior talofibular ligament, on axial images", "Deltoid ligament, on sagittal images", "Calcaneofibular ligament, on sagittal images" ], "answer_index": 1, "explanation": "The ATFL is injured first in inversion sprains and runs horizontally, so axial images show it best.", "subcategory": "Musculoskeletal" }, { "q": "Which plane best shows median nerve swelling and flexor retinaculum bowing in suspected carpal tunnel syndrome?", "options": [ "Oblique coronal", "Coronal", "Axial", "Sagittal" ], "answer_index": 2, "explanation": "Axial images show the carpal tunnel in cross-section, allowing assessment of the median nerve and flexor retinaculum.", "subcategory": "Musculoskeletal" }, { "q": "A baseball pitcher has medial elbow pain. Which plane best shows the ulnar collateral ligament?", "options": [ "Sagittal", "Oblique axial", "Coronal", "Axial" ], "answer_index": 2, "explanation": "The UCL runs along the medial elbow from the medial epicondyle to the sublime tubercle and is best seen on coronal images.", "subcategory": "Musculoskeletal" }, { "q": "On sagittal knee images with 4-5 mm slices, a meniscus shows a continuous 'bow tie' on three or more consecutive slices. This suggests:", "options": [ "A discoid meniscus", "A normal meniscus", "A meniscal cyst", "A bucket-handle tear" ], "answer_index": 0, "explanation": "A normal meniscus shows a bow tie on only about two contiguous 4-5 mm sagittal slices; three or more suggests a discoid meniscus.", "subcategory": "Musculoskeletal" }, { "q": "In a diabetic patient with a foot ulcer, which marrow finding is most specific for osteomyelitis?", "options": [ "Thin cortical line seen only on T2*", "Confluent low T1 signal in the medullary bone next to the ulcer", "Patchy high STIR signal with normal T1 marrow", "Fatty high T1 signal throughout the bone" ], "answer_index": 1, "explanation": "Confluent replacement of normal fatty marrow on T1 is the most specific sign; STIR edema alone may be reactive.", "subcategory": "Musculoskeletal" }, { "q": "A soft-tissue mass follows subcutaneous fat on T1 and T2 and loses signal uniformly with fat suppression, without enhancement. This is most consistent with:", "options": [ "A myxoid liposarcoma", "A peripheral nerve sheath tumor", "A simple lipoma", "A subacute hematoma" ], "answer_index": 2, "explanation": "A lesion matching fat on all sequences and fully suppressing, without nodular enhancement or thick septa, is a simple lipoma.", "subcategory": "Musculoskeletal" }, { "q": "A Morton neuroma is most commonly found in which location?", "options": [ "Under the calcaneal tuberosity", "Between the third and fourth metatarsal heads", "Within the tarsal tunnel", "Between the first and second metatarsal heads" ], "answer_index": 1, "explanation": "Morton neuroma usually forms in the third intermetatarsal space, at the level of the metatarsal heads.", "subcategory": "Musculoskeletal" }, { "q": "On a fat-suppressed T2 coronal oblique shoulder image, which finding indicates a full-thickness supraspinatus tear?", "options": [ "Fluid only in the subacromial-subdeltoid bursa", "High signal within the tendon on short-TE images only", "Tendon thickening with intermediate signal", "Fluid signal extending through the tendon from the bursal to articular surface" ], "answer_index": 3, "explanation": "A full-thickness tear is a fluid-filled defect that spans the tendon from its articular to its bursal surface.", "subcategory": "Musculoskeletal" }, { "q": "A fluid-filled cyst behind the knee extends between which two structures in a Baker (popliteal) cyst?", "options": [ "The lateral head of the gastrocnemius and the biceps femoris", "The medial head of the gastrocnemius and the semimembranosus tendon", "The popliteus tendon and the lateral collateral ligament", "The patellar tendon and the infrapatellar fat pad" ], "answer_index": 1, "explanation": "A Baker cyst communicates with the joint through a neck between the medial gastrocnemius head and the semimembranosus tendon.", "subcategory": "Musculoskeletal" }, { "q": "For suspected sacroiliitis, how are the coronal oblique images of the SI joints prescribed?", "options": [ "Parallel to the iliac crests on a coronal localizer", "Parallel to the long axis of the sacrum on a sagittal image", "Parallel to the table on an axial image", "Perpendicular to the long axis of the sacrum" ], "answer_index": 1, "explanation": "Coronal oblique slices along the sacral long axis show the cartilaginous SI joints best, typically with T1 and STIR.", "subcategory": "Musculoskeletal" }, { "q": "Which plane best shows plantar fascia thickening at its calcaneal attachment in plantar fasciitis?", "options": [ "Sagittal", "Axial", "Oblique axial", "Coronal" ], "answer_index": 0, "explanation": "The plantar fascia runs lengthwise along the sole, so sagittal images show its full length and thickening at the calcaneus.", "subcategory": "Musculoskeletal" } ] } ], "body_regions": [ { "region": "head", "label": "Head / Brain", "common_exams": [ "Routine brain", "Brain for MS", "Brain for seizure", "Pituitary", "Internal auditory canals", "Orbits", "MRA/MRV head", "Brain perfusion", "MR spectroscopy", "CSF flow study" ], "image": { "url": "https://upload.wikimedia.org/wikipedia/commons/e/ef/MRI_Head_Brain_Normal.jpg", "caption": "Normal axial T2-weighted brain MRI at the level of the orbits and midbrain (1.5 T).", "credit": "Ptrump16", "license": "CC BY-SA 4.0", "page_url": "https://commons.wikimedia.org/wiki/File:MRI_Head_Brain_Normal.jpg" }, "questions": [ { "q": "Which sequence is most sensitive to an acute ischemic stroke within the first hours?", "options": [ "T1-weighted spin echo", "Proton-density FSE", "Diffusion-weighted imaging", "Time-of-flight MRA" ], "answer_index": 2, "explanation": "Cytotoxic edema restricts water motion within minutes, so infarcts appear bright on DWI long before T2 changes." }, { "q": "How does FLAIR suppress CSF signal?", "options": [ "A long inversion time nulls CSF before excitation", "A short TE removes CSF signal", "A spectral fat-saturation pulse", "Gradient moment nulling of CSF flow" ], "answer_index": 0, "explanation": "FLAIR is inversion recovery with a TI (~2,000–2,500 ms) timed to CSF's null point, leaving lesions near CSF visible." }, { "q": "In proton MR spectroscopy of the brain, the N-acetylaspartate (NAA) peak at about 2.0 ppm is a marker of:", "options": [ "Cell-membrane turnover", "Anaerobic metabolism", "Myelin-free lipid", "Neuronal integrity" ], "answer_index": 3, "explanation": "NAA is found in neurons, so a lower NAA peak indicates neuronal loss; choline reflects membrane turnover and lactate reflects anaerobic metabolism." } ] }, { "region": "neck", "label": "Neck / Soft Tissue Neck", "common_exams": [ "Soft tissue neck (parotids, thyroid, larynx)", "MRA neck (carotids, vertebrals)", "MRV neck", "Brachial plexus (neck/thoracic inlet)" ], "image": { "url": "https://upload.wikimedia.org/wikipedia/commons/c/c6/Neck_MRI_131151.png", "caption": "Axial MR image through the neck showing the cervical spinal canal, cord, and surrounding soft tissues (case of syringomyelia).", "credit": "Nevit Dilmen", "license": "CC BY-SA 3.0", "page_url": "https://commons.wikimedia.org/wiki/File:Neck_MRI_131151.png" }, "questions": [ { "q": "Spectral fat saturation is patchy across the curved neck. Which technique gives more uniform fat suppression?", "options": [ "Spectral fat saturation with a narrower FOV", "Dixon water–fat separation or STIR", "Gradient echo with a longer TE", "Increasing NEX" ], "answer_index": 1, "explanation": "Air–tissue interfaces and body contour make the field inhomogeneous; Dixon and STIR depend much less on field uniformity." }, { "q": "For 2D time-of-flight MRA of the neck, how should slices be oriented relative to arterial flow?", "options": [ "Parallel to the direction of flow", "Perpendicular to the direction of flow", "At a 45° angle to flow", "Orientation does not affect TOF signal" ], "answer_index": 1, "explanation": "Perpendicular slices let fresh, unsaturated blood flow into each slice and maximize flow-related enhancement." }, { "q": "What is the simplest way to reduce swallowing motion artifact during a soft tissue neck exam?", "options": [ "Increase the slice gap to 100%", "Use a smaller flip angle", "Switch to a head coil", "Coach the patient not to swallow during acquisitions and place a saturation band over the pharynx" ], "answer_index": 3, "explanation": "Patient instructions plus a spatial saturation band suppress signal from moving structures that would otherwise ghost across the image." } ] }, { "region": "chest", "label": "Chest / Thorax & Heart", "common_exams": [ "Cardiac function and viability", "Chest (noncardiac) / mediastinum", "Breast", "Vascular thorax (thoracic aorta MRA)", "Brachial plexus" ], "image": { "url": "https://upload.wikimedia.org/wikipedia/commons/8/86/Cardiac_mri_slice_bionerd.jpg", "caption": "Cardiac MRI four-chamber view showing the heart chambers within the thorax.", "credit": "Bionerd", "license": "CC BY-SA 3.0 / GFDL", "page_url": "https://commons.wikimedia.org/wiki/File:Cardiac_mri_slice_bionerd.jpg" }, "questions": [ { "q": "Which sequence is the standard for cine imaging of ventricular function?", "options": [ "Balanced steady-state free precession (SSFP)", "Conventional spin echo", "STIR", "Diffusion-weighted EPI" ], "answer_index": 0, "explanation": "SSFP gives high SNR and strong blood–myocardium contrast with short TR, making it ideal for cine function studies." }, { "q": "Which part of the ECG waveform is normally used to trigger cardiac MR acquisition?", "options": [ "The P wave", "The T wave", "The R wave", "The U wave" ], "answer_index": 2, "explanation": "The R wave is the largest, most reliable peak; the T wave is distorted in the magnet by the magnetohydrodynamic effect." }, { "q": "A brachial plexus exam needs uniform fat suppression over a large, off-center FOV. Which sequence is most reliable?", "options": [ "Spectral fat-saturated T1", "Opposed-phase GRE", "T1 spin echo without suppression", "STIR" ], "answer_index": 3, "explanation": "STIR suppresses fat by T1 nulling rather than frequency, so it holds up in the inhomogeneous field around the neck and shoulders." } ] }, { "region": "abdomen", "label": "Abdomen", "common_exams": [ "Liver", "Pancreas", "Adrenals", "Kidneys", "MRCP", "MR enterography", "Vascular abdomen (MRA/MRV)" ], "image": { "url": "https://upload.wikimedia.org/wikipedia/commons/thumb/7/7a/Renal_cyst_MRI.jpg/960px-Renal_cyst_MRI.jpg", "caption": "Coronal T2-weighted abdominal MRI showing the liver, kidneys, and a simple left renal cyst (1.5 T).", "credit": "Ptrump16", "license": "CC BY-SA 4.0", "page_url": "https://commons.wikimedia.org/wiki/File:Renal_cyst_MRI.jpg" }, "questions": [ { "q": "At 1.5 T, which TE produces an opposed-phase (out-of-phase) gradient-echo image?", "options": [ "About 4.4 ms", "About 2.2 ms", "About 9 ms", "About 30 ms" ], "answer_index": 1, "explanation": "Fat and water fall out of phase about every 4.4 ms at 1.5 T, first at about 2.2 ms (opposed) and then at 4.4 ms (in phase)." }, { "q": "A patient cannot hold their breath for abdominal T2 imaging. What is the best alternative?", "options": [ "Increase the slice thickness to 15 mm", "Turn off the phase-encoding gradient", "Respiratory triggering with bellows or a navigator echo", "Use a longer TR breath-hold sequence" ], "answer_index": 2, "explanation": "Triggering acquires data at the same point in each breathing cycle, reducing respiratory ghosting without breath-holds." }, { "q": "For a multiphase liver exam, which approach ensures the arterial phase is captured on time?", "options": [ "Bolus tracking or a timing bolus", "A fixed 3-minute delay", "Scanning before the injection only", "Injecting at the slowest possible rate" ], "answer_index": 0, "explanation": "Circulation times vary between patients; monitoring contrast arrival times the late arterial phase precisely." } ] }, { "region": "pelvis", "label": "Pelvis", "common_exams": [ "Female pelvis (uterus, ovaries)", "Male pelvis / prostate (multiparametric)", "Bladder", "Rectum", "Vascular pelvis (MRA/MRV)", "Bony pelvis and hips" ], "image": { "url": "https://upload.wikimedia.org/wikipedia/commons/thumb/d/da/Uterus_arcuatus_als_Zufallsbefund_in_der_MRT_19W_-_MR_PDW_-_001.jpg/960px-Uterus_arcuatus_als_Zufallsbefund_in_der_MRT_19W_-_MR_PDW_-_001.jpg", "caption": "Female pelvis MRI, fat-suppressed PD-weighted axial (top) and coronal (bottom) images showing the uterus and bladder (arcuate uterus).", "credit": "Hellerhoff", "license": "CC BY-SA 4.0", "page_url": "https://commons.wikimedia.org/wiki/File:Uterus_arcuatus_als_Zufallsbefund_in_der_MRT_19W_-_MR_PDW_-_001.jpg" }, "questions": [ { "q": "Which sequence best demonstrates the zonal anatomy of the uterus (endometrium, junctional zone, myometrium)?", "options": [ "T1-weighted spin echo", "Time-of-flight GRE", "T2-weighted FSE", "Opposed-phase GRE" ], "answer_index": 2, "explanation": "On T2W images the endometrium is bright, the junctional zone dark, and the outer myometrium intermediate; T1W shows little zonal contrast." }, { "q": "Why is an antiperistaltic agent (e.g., glucagon) often given for pelvic or bowel MRI?", "options": [ "To reduce bowel motion artifact", "To improve gadolinium enhancement of the uterus", "To decrease SAR", "To distend the bladder" ], "answer_index": 0, "explanation": "Slowing peristalsis reduces ghosting and blurring from moving bowel loops on longer sequences." }, { "q": "In prostate multiparametric MRI, what b-value is recommended for the high-b DWI series?", "options": [ "0 s/mm² only", "About 100 s/mm²", "About 500 s/mm²", "At least 1,400 s/mm²" ], "answer_index": 3, "explanation": "High b-values (≥1,400 s/mm²) suppress normal tissue so that clinically significant cancer stands out as bright." } ] }, { "region": "spine", "label": "Spine", "common_exams": [ "Cervical spine", "Thoracic spine", "Lumbar spine", "Total spine", "Sacrum/coccyx", "SI joints", "Lumbar plexus" ], "image": { "url": "https://upload.wikimedia.org/wikipedia/commons/4/43/Lumbar_MRI_t2-tse-rst-sagittal_06.jpg", "caption": "Sagittal T2-weighted TSE image of the lumbar spine showing vertebral bodies, intervertebral discs, and the CSF-filled thecal sac.", "credit": "Stillwaterising", "license": "CC0", "page_url": "https://commons.wikimedia.org/wiki/File:Lumbar_MRI_t2-tse-rst-sagittal_06.jpg" }, "questions": [ { "q": "Which sequence best shows bone-marrow edema from an acute vertebral compression fracture?", "options": [ "Sagittal T1 without fat suppression", "Sagittal STIR", "Axial gradient echo T2*", "3D time-of-flight" ], "answer_index": 1, "explanation": "STIR suppresses marrow fat so edema in an acute fracture is bright; T1 shows it as dark but with less conspicuity." }, { "q": "When labeling vertebral levels on a thoracic or total spine exam, what is the most reliable method?", "options": [ "Count upward from the lowest rib", "Count from C2 on a large-FOV sagittal localizer that includes the cervical spine", "Assume the conus ends at L1–L2", "Count downward from the aortic arch" ], "answer_index": 1, "explanation": "Thoracic levels are easily mislabeled; counting from C2 on a cervicothoracic localizer avoids wrong-level reporting and surgery." }, { "q": "The iliac crests, often used as an external landmark for lumbar spine positioning, correspond to approximately which level?", "options": [ "T10–T11", "L1–L2", "S2–S3", "L4–L5" ], "answer_index": 3, "explanation": "The intercristal line usually crosses the L4 body or L4–L5 interspace, a common reference for centering the lumbar spine." } ] }, { "region": "upper_extremity", "label": "Upper Extremity", "common_exams": [ "Shoulder", "Shoulder arthrogram", "Elbow", "Wrist", "Hand", "Fingers", "Thumb", "Humerus/forearm (long bones)" ], "image": { "url": "https://upload.wikimedia.org/wikipedia/commons/thumb/4/47/Post_Dislocated_shoulder_MRI_01.png/960px-Post_Dislocated_shoulder_MRI_01.png", "caption": "Shoulder MRI after anterior dislocation showing a Hill-Sachs lesion of the humeral head and a labral Bankart lesion.", "credit": "Hellerhoff", "license": "CC BY-SA 3.0", "page_url": "https://commons.wikimedia.org/wiki/File:Post_Dislocated_shoulder_MRI_01.png" }, "questions": [ { "q": "How should the arm be positioned for a routine shoulder MRI?", "options": [ "At the side in neutral or slight external rotation", "In full internal rotation across the chest", "Abducted overhead", "Flexed 90° at the shoulder" ], "answer_index": 0, "explanation": "Internal rotation makes the supraspinatus and infraspinatus tendons overlap; neutral to slight external rotation lays them out clearly." }, { "q": "Which plane best shows the triangular fibrocartilage complex (TFCC) of the wrist?", "options": [ "Sagittal", "Axial", "Coronal", "Oblique sagittal through the thumb" ], "answer_index": 2, "explanation": "The TFCC spans from the radius to the ulnar styloid, so thin coronal slices show it along its length." }, { "q": "Fat suppression fails on an elbow scanned at the patient's side, far from isocenter. What is the best fix?", "options": [ "Increase the slice gap", "Use a body coil instead of a dedicated coil", "Shorten the TR", "Reposition so the elbow is as close to isocenter as possible (e.g., prone with arm overhead)" ], "answer_index": 3, "explanation": "Field homogeneity is best at isocenter; off-center anatomy suffers from poor spectral fat saturation and lower SNR." } ] }, { "region": "lower_extremity", "label": "Lower Extremity", "common_exams": [ "Hip", "Knee", "Ankle", "Foot", "Femur/tibia (long bones)", "Arthrogram", "Runoff MRA (vascular extremities)" ], "image": { "url": "https://upload.wikimedia.org/wikipedia/commons/d/dc/Knee_MRI_PD_TSE_FS_Sagittal.jpg", "caption": "Sagittal fat-suppressed proton-density TSE image of the knee (1.5 T).", "credit": "Ptrump16", "license": "CC BY-SA 4.0", "page_url": "https://commons.wikimedia.org/wiki/File:Knee_MRI_PD_TSE_FS_Sagittal.jpg" }, "questions": [ { "q": "Which sequence type is preferred for detecting meniscal tears?", "options": [ "Long-TE T2-weighted spin echo only", "Short-TE proton-density weighted FSE", "Time-of-flight GRE", "Diffusion-weighted EPI" ], "answer_index": 1, "explanation": "Short-TE PD images are most sensitive to abnormal signal reaching the meniscal surface; long-TE images miss many tears." }, { "q": "How are sagittal knee slices angled to show the full length of the ACL?", "options": [ "Perpendicular to the patellar tendon", "Exactly parallel to the table edge with no angle", "Parallel to the medial border of the lateral femoral condyle on an axial image", "Parallel to the tibial plateau on a coronal image" ], "answer_index": 2, "explanation": "The ACL runs obliquely from the lateral femoral condyle, so angling sagittals along that condyle shows the ligament in one or two slices." }, { "q": "In moving-table (bolus-chase) runoff MRA, which station is typically acquired first?", "options": [ "The aortoiliac (abdomen/pelvis) station", "The calf/foot station", "The thigh station", "All stations at once" ], "answer_index": 0, "explanation": "The bolus reaches the aorta first, so imaging moves from the aortoiliac station down the legs ahead of venous enhancement." } ] } ] }