{ "modality": "CT", "spec_basis": "ARRT CT Examination Content Specifications, Board approved July 2025, effective September 1, 2026 (current; replaced the 2022 specifications in effect through August 31, 2026). 195-minute test time and 30 pilot items per ARRT 2026 Postprimary Eligibility Pathway Handbook.", "how_to_use": "Procedures carries the most questions (71 of 165, about 43%), so learn protocols, contrast timing and cross-sectional anatomy first, then Image Production (52, about 32%), especially reconstruction, windowing, artifacts and QC. Patient Care and Safety (21 each, about 13%) are smaller but very testable: contrast reactions, renal screening, dose metrics and dose-reduction factors. Finish with the last-minute review list.", "chapters": [ { "id": "patient-care", "category": "Patient Care", "scored_questions": 21, "weight_pct": 12.7, "topics": [ { "subcategory": "Patient Interactions and Management", "title": "Screening, history and lab values", "must_know": [ "Before IV iodinated contrast, screen for prior contrast reaction, renal disease, diabetes/metformin, pregnancy, and thyroid disease.", "eGFR is the preferred renal screen; ACR treats eGFR below 30 mL/min/1.73 m2 or any acute kidney injury as the high-risk group for contrast-associated AKI.", "Coagulation labs (PT/INR, PTT, platelets) are checked before biopsy, drainage and other invasive procedures to judge bleeding risk.", "A negative D-dimer in a low-probability patient helps exclude PE; an elevated D-dimer is nonspecific.", "Elevated WBC suggests infection or inflammation (e.g., appendicitis, abscess); low hemoglobin suggests blood loss or anemia; abnormal LFTs point to liver or biliary disease.", "Schedule CT before barium fluoroscopy, because retained barium causes streak artifact; schedule thyroid radioactive iodine studies or therapy before iodinated contrast, which can block iodine uptake for weeks.", "Uncontrolled hyperthyroidism is a caution for iodinated contrast because of the risk of thyrotoxicosis." ], "memory_tip": "Kidneys = eGFR; bleeding = INR/PTT/platelets; clot = D-dimer; infection = WBC; pregnancy = hCG.", "board_traps": [ "Serum creatinine alone is not the ACR-preferred measure; eGFR is.", "D-dimer cannot confirm PE; it is used to rule it out.", "A recent barium study is a scheduling problem for abdominal CT, not a contraindication to CT." ], "key_numbers": [ { "label": "Serum creatinine (adult)", "value": "about 0.6-1.2 mg/dL" }, { "label": "BUN", "value": "about 7-20 mg/dL" }, { "label": "High-risk eGFR (ACR)", "value": "< 30 mL/min/1.73 m2" }, { "label": "Platelets", "value": "150,000-400,000 per microliter" }, { "label": "INR (not anticoagulated)", "value": "about 0.8-1.1" }, { "label": "PT", "value": "about 11-13.5 s" }, { "label": "PTT", "value": "about 25-35 s" }, { "label": "WBC", "value": "about 4,500-11,000 per microliter" } ] }, { "subcategory": "Patient Interactions and Management", "title": "Consent, communication, time-out and safe handling", "must_know": [ "Informed consent (risks, benefits, alternatives) is required for invasive procedures such as CT-guided biopsy and is obtained by the provider performing it; the patient must be competent and of legal age, or a legal representative signs.", "Implied consent applies to an unconscious patient in an emergency; oral consent is acceptable for routine low-risk care.", "Use at least two patient identifiers (e.g., name and date of birth); never use room number.", "A time-out immediately before an invasive procedure confirms correct patient, procedure and site/side with the whole team.", "Remove radiopaque objects from the scan range (jewelry, hairpins, dentures, underwire bras, snaps); keep insulin pumps and glucose monitors out of the beam per manufacturer guidance, and minimize direct beam time over pacemakers and neurostimulators.", "For transfers: lock wheels, use slide boards or lift devices, keep a wide base of support, bend the knees and keep the load close.", "Use positioning aids (straps, sponges, wedges) for immobilization and comfort; restraints require an order and policy compliance." ], "memory_tip": "Time-out = right patient, right procedure, right site, said out loud by everyone.", "board_traps": [ "The technologist does not obtain informed consent for a biopsy; the physician/provider does.", "A patient who has received sedation cannot then give valid informed consent." ], "key_numbers": [] }, { "subcategory": "Patient Interactions and Management", "title": "Patient monitoring and accessory devices", "must_know": [ "Monitor level of consciousness, vital signs, ECG and oxygen saturation during contrast, sedation and invasive procedures; know where the crash cart is and how to call a code.", "The Glasgow Coma Scale ranges from 3 to 15; a score of 8 or less indicates severe impairment.", "ECG: P wave = atrial depolarization, QRS = ventricular depolarization, T wave = ventricular repolarization; cardiac gating triggers off the R wave.", "Oxygen: nasal cannula about 1-6 L/min, simple mask about 6-10 L/min, nonrebreather about 10-15 L/min.", "Keep chest tube drainage units and Foley bags below the level of the chest/bladder, avoid kinks, and do not clamp unless ordered.", "Fall prevention: assist on and off the table, use side rails/straps, and never leave a fall-risk or sedated patient unattended." ], "memory_tip": null, "board_traps": [ "Raising a urine bag above the bladder causes reflux; it must stay below.", "SpO2 below about 90-92% is not normal and needs action." ], "key_numbers": [ { "label": "Adult heart rate", "value": "60-100 bpm" }, { "label": "Adult respiratory rate", "value": "12-20 breaths/min" }, { "label": "Normal SpO2", "value": "about 95-100%" }, { "label": "Normal adult BP", "value": "below 120/80 mm Hg" }, { "label": "Normal oral temperature", "value": "about 98.6 F (37 C)" } ] }, { "subcategory": "Patient Interactions and Management", "title": "Contrast media types and special considerations", "must_know": [ "Nonionic contrast does not dissociate in solution, so it has lower osmolality and fewer adverse effects than ionic high-osmolality contrast.", "Osmolality: HOCM is several times plasma, LOCM is about 2-3 times plasma, IOCM (iodixanol) matches plasma at about 290 mOsm/kg.", "Warming iodinated contrast to body temperature (37 C) lowers viscosity, which helps high flow rates through small catheters.", "Barium sulfate is contraindicated when bowel perforation is suspected or before surgery; use water-soluble iodinated oral or rectal contrast instead.", "Hyperosmolar water-soluble oral agents can cause pulmonary edema if aspirated, so aspiration risk matters when choosing oral contrast.", "Negative contrast = air or CO2 (colonography); neutral contrast = water or low-density barium (enterography, stomach, pancreas protocols).", "Pregnancy: iodinated contrast crosses the placenta and is given only when the information is needed and cannot be obtained otherwise. Lactation: ACR says breastfeeding need not be interrupted.", "Dialysis: per ACR, patients on dialysis can receive iodinated contrast without scheduling urgent post-contrast dialysis; anuric patients have no remaining kidney function to protect." ], "memory_tip": "The lower the osmolality, the closer to blood and the fewer the side effects: HOCM > LOCM > IOCM (equal to plasma).", "board_traps": [ "Iodixanol is iso-osmolar but more viscous; iso-osmolar does not mean low viscosity.", "Shellfish allergy is not a specific contraindication to iodinated contrast; a prior reaction to contrast is the strongest predictor." ], "key_numbers": [ { "label": "Plasma osmolality", "value": "about 290 mOsm/kg" }, { "label": "Iodine dose", "value": "concentration (mg I/mL) x volume, e.g., 350 mg I/mL x 100 mL = 35 g I" } ] }, { "subcategory": "Patient Interactions and Management", "title": "Medications, routes and metformin", "must_know": [ "Metformin: per ACR, hold at the time of contrast and for 48 hours after only in patients with AKI or eGFR below 30, restarting after renal function is rechecked; others need not stop.", "Lidocaine is the local anesthetic for biopsies and drain placement.", "Metoprolol (beta-blocker) lowers heart rate for coronary CTA; contraindications include asthma/active bronchospasm, hypotension, high-grade heart block and decompensated heart failure.", "Sublingual nitroglycerin dilates coronary arteries for CCTA; it is contraindicated with hypotension and recent PDE-5 inhibitor use (e.g., sildenafil, tadalafil).", "tPA (alteplase) dissolves clots in acute ischemic stroke and is given only after noncontrast head CT excludes hemorrhage, within the treatment window from last known well.", "Glucagon reduces bowel peristalsis for enterography or colonography; avoid in pheochromocytoma and insulinoma.", "Intrathecal injection (myelography) must use an agent labeled for intrathecal use (e.g., certain iohexol or iopamidol formulations); ionic contrast given intrathecally can be fatal.", "Other routes: oral, rectal (enema tip/catheter), Foley catheter (cystogram, by gravity), intra-articular (arthrogram), stoma." ], "memory_tip": "Metoprolol slows, nitro opens: beta-blocker for heart rate, nitro for vessel size.", "board_traps": [ "Metformin does not need to be held for every contrast patient; only AKI or eGFR < 30.", "tPA is never given before CT rules out a bleed.", "An ionic or non-intrathecal agent in a myelogram syringe is a never-event." ], "key_numbers": [ { "label": "tPA window (ischemic stroke)", "value": "up to 4.5 h from last known well" }, { "label": "Metformin hold (high-risk only)", "value": "48 h after contrast" }, { "label": "Pediatric IV contrast (typical)", "value": "weight-based, about 1.5-2 mL/kg" } ] }, { "subcategory": "Patient Interactions and Management", "title": "Venipuncture and power injection", "must_know": [ "Prefer an antecubital vein with an 18-20 gauge catheter for flow rates of about 3-5 mL/s; a 22 gauge is generally limited to lower rates (about 3 mL/s or less).", "Avoid the arm on the side of a mastectomy/lymph node dissection, a dialysis fistula or graft, an existing infusion, or a prior infiltration site.", "Do not power inject through butterfly needles; use central lines, PICCs or implanted ports only if labeled power-injectable and within their rated flow and pressure (ports need a power-rated non-coring needle).", "Document site, gauge, number of attempts, contrast agent, concentration, volume and flow rate.", "Single-head injectors deliver contrast only; dual-head add a saline chaser that pushes the bolus centrally, lowers contrast volume and reduces streak artifact in the arm and SVC; syringeless injectors use a bulk reservoir with single-patient tubing.", "Multiphase (biphasic or split-bolus) injections vary rate or volume in programmed phases; the pressure limit (psi) protects the catheter.", "Purge all air from syringes and tubing; for suspected venous air embolism, place the patient left side down with head down and give oxygen." ], "memory_tip": "Bigger rate needs a bigger needle: 18-20 g for 4-5 mL/s.", "board_traps": [ "A PICC is not automatically power-injectable; check the label/hub.", "A smaller gauge number means a larger needle." ], "key_numbers": [ { "label": "High-rate IV size", "value": "18-20 gauge" }, { "label": "Contrast volume", "value": "flow rate x injection time, e.g., 4 mL/s x 25 s = 100 mL" } ] }, { "subcategory": "Patient Interactions and Management", "title": "Scan timing and contrast reactions", "must_know": [ "Bolus tracking places an ROI in the target vessel and triggers the scan when a preset HU threshold is reached; a timing (test) bolus measures time-to-peak with a small injection to set the delay.", "Mild reactions: limited hives, itching, nasal congestion, sneezing. Moderate: diffuse hives, bronchospasm without hypoxia, facial edema without dyspnea. Severe: laryngeal edema, severe bronchospasm, anaphylactic shock, cardiopulmonary arrest.", "Physiologic effects (warmth, metallic taste, transient nausea) are not allergic-like and do not require premedication.", "Epinephrine is first-line for severe allergic-like reactions; adult IM dose is 0.3 mg of 1 mg/mL into the anterolateral thigh, repeatable.", "Hives: observe or diphenhydramine; bronchospasm: oxygen plus albuterol inhaler; hypotension with tachycardia: leg elevation, IV fluids, epinephrine.", "Vasovagal reaction = hypotension with bradycardia: elevate legs, oxygen, IV fluids, atropine if it persists.", "Premedication for prior allergic-like reaction (ACR): prednisone 50 mg at 13, 7 and 1 h before plus diphenhydramine 50 mg 1 h before, or methylprednisolone 32 mg at 12 and 2 h before; breakthrough reactions can still occur." ], "memory_tip": "Slow and low (bradycardia + hypotension) = vasovagal = atropine. Fast and low (tachycardia + hypotension) = anaphylactoid = epinephrine.", "board_traps": [ "Diphenhydramine causes drowsiness: the patient must not drive afterward.", "Bolus tracking ROI goes in the vessel of interest (e.g., main pulmonary artery for PE), not in the injected arm." ], "key_numbers": [ { "label": "Epinephrine IM (adult)", "value": "0.3 mg of 1 mg/mL" }, { "label": "Atropine IV (adult, ACR)", "value": "0.6-1 mg, up to 3 mg total" }, { "label": "Oxygen for reactions", "value": "6-10 L/min by mask" }, { "label": "Diphenhydramine", "value": "25-50 mg" } ] }, { "subcategory": "Patient Interactions and Management", "title": "Post-procedure care, extravasation and infection control", "must_know": [ "Extravasation: stop the injection, notify the radiologist, elevate the limb, apply compresses per policy, document, and follow up; most resolve without injury.", "Signs of compartment syndrome or serious injury after extravasation (increasing pain or swelling, altered perfusion, changed sensation, blistering) need prompt surgical consultation.", "Delayed contrast reactions, usually skin rashes, can appear hours to about a week later; tell patients what to watch for.", "Standard precautions apply to every patient; add contact (gown, gloves), droplet (mask) or airborne (N95, negative-pressure room) precautions by disease.", "C. difficile spores resist alcohol: wash hands with soap and water and clean with a sporicidal (bleach-based) disinfectant.", "Sterilization kills all microorganisms including spores (needed for items entering sterile tissue); disinfection kills most but not all spores; clean the table and gantry between patients." ], "memory_tip": "Airborne = MTV: measles, TB, varicella, so N95.", "board_traps": [ "Alcohol hand rub is not adequate for C. difficile.", "Influenza is droplet, not airborne, for routine precautions." ], "key_numbers": [] } ] }, { "id": "safety", "category": "Safety", "scored_questions": 21, "weight_pct": 12.7, "topics": [ { "subcategory": "Radiation Safety and Dose", "title": "X-ray production and target interactions", "must_know": [ "Thermionic emission boils electrons off the cathode filament; they are accelerated by kVp to the rotating tungsten anode.", "Over 99% of the electron energy becomes heat and under 1% becomes x-rays, so CT tubes need high heat capacity and cooling.", "Bremsstrahlung (braking) radiation makes most of the diagnostic beam and gives a continuous energy spectrum.", "Characteristic radiation arises when an incident electron ejects an inner-shell electron; tungsten K-characteristic x-rays need kVp above 69.5 kV.", "The CT beam is polyenergetic; its maximum photon energy in keV equals the kVp setting.", "SI units are the primary units on the CT exam: gray (Gy) for absorbed dose, sievert (Sv) for effective dose." ], "memory_tip": "Brems = brakes: electron slows near the nucleus, makes most of the beam.", "board_traps": [ "Characteristic x-ray energy depends on the target material, not on kVp.", "Raising mA increases the number of photons, not their energy." ], "key_numbers": [ { "label": "Tungsten K-shell binding energy", "value": "69.5 keV" }, { "label": "Heat vs x-ray", "value": ">99% heat, <1% x-rays" }, { "label": "1 Gy", "value": "100 rad" }, { "label": "1 Sv", "value": "100 rem" } ] }, { "subcategory": "Radiation Safety and Dose", "title": "Beam characteristics and photon interactions", "must_know": [ "X-rays travel at the speed of light, have no mass or charge, and energy rises with frequency while wavelength falls.", "Beam quality (penetrating power) is set by kVp and filtration; beam quantity (number of photons) is set by mAs.", "Inverse square law: intensity changes with 1/distance squared; doubling distance gives one-quarter the intensity.", "Photoelectric absorption: inner-shell, total absorption; probability rises sharply with atomic number (about Z cubed) and falls with energy; it creates contrast and adds patient dose.", "Compton scatter: outer-shell interaction that dominates in soft tissue at CT energies and is the main source of scatter dose to staff.", "Coherent (classical) scatter does not ionize and is a small fraction at CT energies.", "Iodine and barium attenuate strongly because their K-edges (33.2 and 37.4 keV) sit near the mean energy of a low-kVp beam." ], "memory_tip": "Photoelectric = Picture contrast + Patient dose; Compton = sCatter to the Crew.", "board_traps": [ "Remnant (exit) radiation forms the image; primary beam is what leaves the tube.", "Compton probability depends on electron density, not strongly on atomic number." ], "key_numbers": [ { "label": "Iodine K-edge", "value": "33.2 keV" }, { "label": "Barium K-edge", "value": "37.4 keV" }, { "label": "Inverse square", "value": "I1/I2 = (D2/D1)^2" } ] }, { "subcategory": "Radiation Safety and Dose", "title": "Technical factors that lower patient dose", "must_know": [ "Dose is directly proportional to mAs; halving mAs halves dose but raises noise by about 41%.", "Dose rises steeply with kVp (roughly with the square); lowering kVp (e.g., 120 to 100 or 80) cuts dose and boosts iodine contrast in small patients and CTA.", "At constant mA and rotation time, increasing pitch lowers dose; on systems that hold effective mAs (mAs/pitch) constant, the scanner raises mA to compensate.", "Wider beam collimation is more dose-efficient because overbeaming (penumbra) is a smaller share of the beam; very narrow beams waste more dose.", "Over-ranging adds extra exposure at the start and end of a helical scan; it grows with wider beams and higher pitch and is reduced by adaptive (dynamic) collimators.", "Bowtie filters and added filtration remove low-energy photons and reduce dose to the periphery.", "Iterative and deep-learning reconstruction lower noise, allowing lower-dose acquisitions; prospective ECG gating gives far lower dose than retrospective gating." ], "memory_tip": null, "board_traps": [ "Increasing pitch does not always lower dose: auto-mA or effective-mAs systems raise mA to keep noise constant.", "Thinner reconstructed slices do not add dose; they add noise." ], "key_numbers": [ { "label": "Effective mAs", "value": "mA x rotation time / pitch" }, { "label": "Noise vs mAs", "value": "noise proportional to 1 / square root of mAs" } ] }, { "subcategory": "Radiation Safety and Dose", "title": "Automatic exposure control and patient considerations", "must_know": [ "Tube current modulation varies mA by angle (x-y) and along the z-axis from the localizer, matching dose to patient thickness. Vendor names: SmartmA/AutomA (GE), CARE Dose4D (Siemens), SURE Exposure (Canon), DoseRight (Philips).", "Center the patient at gantry isocenter; off-center positioning distorts localizer size estimates and bowtie filtering, raising dose or noise.", "The localizer must cover the whole planned scan range for z-axis modulation to work.", "A higher GE noise index lowers dose; a higher Siemens quality reference mAs raises dose.", "Pediatric: size- or weight-based protocols, lower kVp and mAs, scan only the needed region (Image Gently); adults: Image Wisely.", "Clear breathing instructions prevent repeat scans; justification (right exam) and optimization (ALARA) are the core principles.", "Pregnancy: confirm status, justify, and optimize; ACOG states fetal doses below 50 mGy are not associated with anomalies or pregnancy loss." ], "memory_tip": "Noise index up = dose down (GE). Reference mAs up = dose up (Siemens).", "board_traps": [ "Routine patient gonadal or fetal shielding is no longer recommended by AAPM and NCRP; in-plane shields can disturb AEC and cause artifacts, so follow facility policy.", "Placing a patient too low in the gantry is not harmless; it alters modulation and dose." ], "key_numbers": [ { "label": "Fetal dose without increased anomaly risk (ACOG)", "value": "< 50 mGy" } ] }, { "subcategory": "Radiation Safety and Dose", "title": "Dose metrics and documentation", "must_know": [ "Absorbed dose (Gy) is energy per mass (J/kg); effective dose (Sv) weights organ doses by tissue sensitivity for whole-body risk.", "CTDIw = 1/3 center + 2/3 periphery measured in a 16 cm (head) or 32 cm (body) PMMA phantom; CTDIvol = CTDIw / pitch.", "DLP = CTDIvol x scan length (mGy-cm); lengthening the scan raises DLP but not CTDIvol.", "CTDIvol is a scanner output index, not the patient's dose; size-specific dose estimate (SSDE) adjusts it for patient size.", "Estimated effective dose = DLP x k factor for the body region.", "Dose notification warns before scanning when a planned series exceeds a set CTDIvol/DLP; a dose alert warns when the cumulative exam value would exceed a higher threshold and requires a reason to proceed.", "Record CTDIvol and DLP for each exam (Joint Commission requirement) and report scanning errors (wrong patient, wrong exam, excess dose) through the facility adverse event process." ], "memory_tip": "CTDIvol = per slice intensity; DLP = intensity x length.", "board_traps": [ "A small patient scanned in the 32 cm phantom reference receives more dose than CTDIvol shows; SSDE corrects this.", "Effective dose from DLP is an estimate for populations, not an individual patient's risk." ], "key_numbers": [ { "label": "k factor head", "value": "0.0021 mSv/(mGy-cm)" }, { "label": "k factor chest", "value": "0.014 mSv/(mGy-cm)" }, { "label": "k factor abdomen-pelvis", "value": "0.015 mSv/(mGy-cm)" }, { "label": "AAPM suggested notification, adult head", "value": "CTDIvol 80 mGy" }, { "label": "AAPM suggested notification, brain perfusion", "value": "CTDIvol 600 mGy" }, { "label": "AAPM suggested alert value", "value": "CTDIvol 1000 mGy" } ] }, { "subcategory": "Radiation Safety and Dose", "title": "Personnel protection", "must_know": [ "Cardinal principles: minimize time, maximize distance, use shielding.", "Stay outside the room during exposure with the door closed; controlled-access warning signs and lights limit entry.", "If someone must hold a patient, use a non-pregnant family member or caregiver (not staff), with a lead apron, standing away from the scan plane.", "Scatter is greatest near the gantry opening in the scan plane and falls off with distance.", "During CT fluoroscopy, use needle holders, low mA and intermittent short exposures, and keep hands out of the beam.", "Wear the dosimeter at the collar outside the apron when wearing lead; occupational dose limits follow NCRP recommendations." ], "memory_tip": null, "board_traps": [ "Staff should not routinely hold patients during scanning.", "For x-rays the radiation weighting factor is 1, so 1 Gy absorbed dose equals 1 Sv equivalent dose." ], "key_numbers": [ { "label": "Occupational effective dose limit (NCRP)", "value": "50 mSv/yr" }, { "label": "Cumulative occupational limit (NCRP)", "value": "10 mSv x age in years" }, { "label": "Embryo/fetus of pregnant worker", "value": "0.5 mSv per month" }, { "label": "General public (frequent)", "value": "1 mSv/yr" }, { "label": "Lens of eye (NCRP Commentary 26)", "value": "50 mGy/yr recommended, down from 150 mSv" } ] } ] }, { "id": "image-production", "category": "Image Production", "scored_questions": 52, "weight_pct": 31.5, "topics": [ { "subcategory": "Image Formation", "title": "Gantry and system components", "must_know": [ "Third-generation (rotate-rotate) design, with tube and curved detector array rotating together, is the standard modern geometry; fourth generation used a stationary detector ring.", "Slip rings allow continuous rotation, which made helical scanning possible.", "The high-frequency generator in the gantry supplies stable high voltage; CT tubes use rotating anodes with very high heat capacity.", "Solid-state detectors use a scintillator that converts x-rays to light and a photodiode that converts light to an electrical signal; photon-counting detectors convert x-rays directly and sort photons by energy.", "The data acquisition system (DAS) amplifies detector signals, applies log conversion and digitizes them with an analog-to-digital converter.", "Prepatient (source) collimation sets beam width and patient dose; postpatient collimation or anti-scatter grids reduce scatter reaching detectors.", "In multidetector CT the detector row configuration sets acquisition slice thickness: total beam collimation = number of channels x channel width.", "The array processor performs the reconstruction math; the host computer runs the system and operator interface." ], "memory_tip": "DAS = Digitize And Send.", "board_traps": [ "Prepatient collimation controls dose; postpatient collimation does not reduce patient dose.", "Ring artifacts are a third-generation (rotate-rotate) problem from a bad detector element." ], "key_numbers": [ { "label": "Example beam collimation", "value": "64 x 0.625 mm = 40 mm" }, { "label": "Standard bore", "value": "about 70 cm (wide bore about 80 cm or more)" } ] }, { "subcategory": "Image Formation", "title": "kVp, mAs and noise", "must_know": [ "kVp controls beam energy and penetration; lower kVp raises iodine conspicuity and lowers dose but increases noise, especially in large patients.", "mAs controls photon quantity and noise; noise is inversely proportional to the square root of mAs.", "Doubling mAs reduces noise by about 29%; halving noise requires four times the mAs.", "Faster rotation improves temporal resolution but lowers mAs per rotation unless mA is raised.", "Large patients need higher kVp/mAs to avoid photon starvation streaks; children need lower settings." ], "memory_tip": "To halve noise, quadruple mAs (square root rule).", "board_traps": [ "Doubling mAs does not halve noise.", "kVp, not mAs, changes beam penetration and image contrast." ], "key_numbers": [ { "label": "Noise relationship", "value": "noise proportional to 1 / sqrt(mAs)" }, { "label": "Typical kVp range", "value": "about 70-140 kVp" } ] }, { "subcategory": "Image Formation", "title": "Pitch, collimation, planes and SFOV", "must_know": [ "Pitch = table travel per rotation / total beam collimation (e.g., 60 mm travel with 40 mm beam = 1.5).", "Pitch 1 is contiguous; above 1 leaves gaps filled by interpolation (faster, lower dose); below 1 overlaps data (higher dose, used in cardiac gating).", "Table speed = pitch x beam collimation / rotation time; scan time = scan length / table speed.", "Axes: x = left-right, y = anterior-posterior, z = long axis of the table; axial images lie in the x-y plane.", "Scan field of view (SFOV) sets the region measured and the bowtie filter; it must be at least as large as the body part to avoid out-of-field artifact.", "Display field of view (DFOV) is chosen at reconstruction and cannot exceed the SFOV." ], "memory_tip": "Pitch: travel over beam. Over 1 = gaps, under 1 = overlap.", "board_traps": [ "The z-axis runs along the patient's length, not front-to-back.", "DFOV can be changed retrospectively from raw data; SFOV cannot be changed after scanning." ], "key_numbers": [ { "label": "Pitch formula", "value": "table feed per rotation / total beam width" }, { "label": "Example", "value": "40 mm beam, 60 mm/rotation = pitch 1.5" } ] }, { "subcategory": "Image Formation", "title": "Methods of data acquisition", "must_know": [ "Sequential (step-and-shoot): table stops for each exposure, then moves; used for HRCT, some head protocols and prospective cardiac gating.", "Helical: continuous rotation with continuous table motion produces a volume dataset that needs z-axis interpolation.", "Volumetric (wide-detector, up to about 16 cm coverage) imaging covers an organ such as the heart or brain in one rotation without table motion.", "Cine scans one location repeatedly with no table motion; shuttle mode moves the table back and forth to extend perfusion coverage; CT fluoroscopy gives near-real-time images for interventions.", "Dual energy uses two spectra (dual source, rapid kV switching, dual-layer detector or split filter) to create virtual monoenergetic images, iodine maps and virtual noncontrast images and to separate uric acid from calcium stones.", "Dual-source scanners (two tubes about 90 degrees apart) improve temporal resolution to about a quarter rotation and allow very high-pitch scanning." ], "memory_tip": null, "board_traps": [ "Cine/perfusion scanning repeats the same location, so local dose builds up quickly.", "Low-keV virtual monoenergetic images increase iodine contrast; high-keV images reduce metal and beam-hardening artifact." ], "key_numbers": [] }, { "subcategory": "Image Formation", "title": "Image reconstruction", "must_know": [ "Raw (projection) data allow changes to kernel, slice thickness, interval, DFOV and center; image data only allow windowing, zoom and reformatting.", "Filtered backprojection applies a convolution filter to remove the blur of simple backprojection; fast but noisier at low dose.", "Iterative reconstruction repeatedly compares projected estimates with measured data to cut noise and artifacts, permitting lower dose; deep-learning reconstruction is a newer option.", "Sharp (high spatial frequency) kernels such as bone or lung improve edge detail but increase noise; smooth (soft tissue) kernels lower noise and favor contrast resolution.", "Reconstructed slice thickness cannot be thinner than acquisition thickness; thinner slices reduce partial volume but increase noise.", "Reconstruction interval is the spacing between image centers; overlapping (e.g., 50%) images improve MPR and 3D quality with no added dose.", "180-degree linear interpolation gives a thinner effective slice than 360-degree interpolation but more noise.", "Prospective reconstruction uses parameters set before the scan; retrospective reconstruction later reprocesses the saved raw data." ], "memory_tip": "Raw data = recipe ingredients (can re-cook); image data = the finished dish (can only re-plate).", "board_traps": [ "Overlapping reconstructions do not increase patient dose.", "Once raw data are purged, a new kernel or thinner slices cannot be made." ], "key_numbers": [ { "label": "Common overlap", "value": "interval about half the slice thickness" } ] }, { "subcategory": "Image Formation", "title": "Postprocessing and quantitative tools", "must_know": [ "MPR creates coronal, sagittal and oblique planes; curved planar reformation follows a curved structure such as a vessel, ureter or mandible.", "Isotropic voxels (equal in x, y, z) give reformats with the same resolution as axial images.", "MIP shows the highest-attenuation voxel along each ray (vessels, nodules) but loses depth, and dense calcium can hide the lumen; MinIP shows the lowest (airways, emphysema).", "Shaded surface display uses a single threshold to show surfaces only; volume rendering assigns color and opacity to all voxels and uses the full dataset.", "Measurement tools give distance, diameter, area, volume and ROI mean HU and SD.", "Agatston calcium scoring counts lesions of at least 130 HU and multiplies area by a density factor: 1 (130-199), 2 (200-299), 3 (300-399), 4 (400 or more)." ], "memory_tip": "MIP = Maximum (bright vessels); MinIP = Minimum (dark airways).", "board_traps": [ "MIP is not the best choice for showing a calcified vessel lumen; calcium dominates.", "SSD discards most of the data; volume rendering keeps it." ], "key_numbers": [ { "label": "Calcium scoring threshold", "value": "130 HU" } ] }, { "subcategory": "Image Evaluation and Archiving", "title": "Pixels, matrix, DFOV and windowing", "must_know": [ "A pixel is a 2D picture element; a voxel adds slice thickness as depth.", "Pixel size = DFOV / matrix (e.g., 250 mm / 512 = about 0.49 mm); a smaller DFOV with the same matrix gives smaller pixels and better spatial resolution.", "Zooming image data enlarges pixels without improving resolution; targeted reconstruction from raw data with a smaller DFOV does improve it.", "Window width (WW) sets the range of HU shown in gray; window level (WL) is its center. Displayed range = WL +/- WW/2.", "Narrow WW = high contrast (brain, liver); wide WW = low contrast with long gray scale (lung, bone).", "Raising WL makes the image darker; lowering WL makes it brighter.", "Cine loops scroll through stacks or display dynamic data such as cardiac phases." ], "memory_tip": "Level is the middle, width is the spread; anything above the top is white, below the bottom is black.", "board_traps": [ "Magnification (zoom) does not equal targeted reconstruction.", "Increasing window level darkens, not brightens." ], "key_numbers": [ { "label": "Window example", "value": "WW 400 / WL 40 shows -160 to +240 HU" }, { "label": "Brain", "value": "about WW 80 / WL 40" }, { "label": "Soft tissue abdomen", "value": "about WW 350-400 / WL 40-50" }, { "label": "Lung", "value": "about WW 1500 / WL -600" }, { "label": "Bone", "value": "about WW 2000 / WL 300-500" } ] }, { "subcategory": "Image Evaluation and Archiving", "title": "CT numbers and ROI measurement", "must_know": [ "HU = 1000 x (mu tissue - mu water) / mu water; water is 0 and air is -1000 by definition.", "An ROI reports mean HU and standard deviation; the SD is a measure of noise.", "Enhancement greater than about 20 HU after contrast indicates true enhancement; 10-20 HU is indeterminate.", "Macroscopic fat (negative HU) in a renal mass indicates angiomyolipoma; noncontrast adrenal nodule of 10 HU or less suggests lipid-rich adenoma.", "Acute blood is hyperdense compared with brain; simple fluid measures near water.", "Beam hardening can falsely raise cyst HU (pseudoenhancement), especially in small renal cysts." ], "memory_tip": "Air -1000, fat about -100, water 0, soft tissue +40, bone up to +1000 and above.", "board_traps": [ "Fat is negative but far above air; do not confuse -100 with -1000.", "A high SD means noise, not enhancement." ], "key_numbers": [ { "label": "Air", "value": "-1000 HU" }, { "label": "Lung", "value": "about -700 to -900 HU" }, { "label": "Fat", "value": "about -100 to -50 HU" }, { "label": "Water", "value": "0 HU" }, { "label": "Simple cyst/CSF", "value": "about 0-20 HU" }, { "label": "Soft tissue/muscle", "value": "about +40 to +60 HU" }, { "label": "Acute hemorrhage", "value": "about +50 to +80 HU" }, { "label": "Bone", "value": "about +400 to +1000 or more HU" } ] }, { "subcategory": "Image Evaluation and Archiving", "title": "Image quality: resolution, noise and linearity", "must_know": [ "Spatial resolution (lp/cm, MTF, bar pattern) improves with small focal spot, small detector elements, small pixels, thin slices, sharp kernel and no motion.", "Contrast resolution (low-contrast detectability) depends mainly on noise, so higher mAs, thicker slices and smooth kernels improve it.", "Temporal resolution depends on rotation time; half-scan reconstruction needs about half a rotation, dual-source about a quarter.", "Noise is the SD of HU in a uniform region; uniformity means a water phantom reads the same HU at center and edge.", "Linearity means measured HU track known attenuation in a phantom with several materials (air, polyethylene, water, acrylic, bone-equivalent)." ], "memory_tip": null, "board_traps": [ "Thinner slices improve spatial (z) resolution but worsen noise and low-contrast detectability.", "Temporal resolution is about time, not slice thickness." ], "key_numbers": [] }, { "subcategory": "Image Evaluation and Archiving", "title": "QA/QC, accreditation and tube warm-up", "must_know": [ "Daily QC (technologist): water phantom CT number, noise, uniformity and artifact check; air calibration per manufacturer.", "Additional periodic tests include slice thickness, laser/table alignment, table increment accuracy, linearity, spatial and low-contrast resolution; a medical physicist surveys annually.", "ACR CT phantom modules test alignment, CT number and slice thickness; low contrast; uniformity, noise and distance; and high-contrast (spatial) resolution.", "Medicare (MIPPA) requires accreditation for outpatient advanced imaging billed under the physician fee schedule, through ACR, IAC or The Joint Commission; ACR accreditation runs on a 3-year cycle.", "Warm the tube at the start of the day and after idle periods per the manufacturer to avoid thermal stress and cracking of a cold anode." ], "memory_tip": null, "board_traps": [ "Daily water CT number drift is a calibration issue to fix before patients, not to ignore.", "Accreditation is not the same as state registration of the unit." ], "key_numbers": [ { "label": "Water CT number (ACR criterion)", "value": "0 +/- 7 HU" }, { "label": "Uniformity (ACR criterion)", "value": "edge within +/- 5 HU of center" }, { "label": "ACR accreditation dose limit, adult head", "value": "CTDIvol 80 mGy" }, { "label": "ACR accreditation dose limit, adult abdomen", "value": "CTDIvol 30 mGy" } ] }, { "subcategory": "Image Evaluation and Archiving", "title": "Patient-related artifacts", "must_know": [ "Beam hardening: dark streaks between dense structures (e.g., between petrous bones in the posterior fossa) and cupping (center reads lower); reduced by bowtie filters, correction software and higher kVp.", "Partial volume averaging: tissues of different density averaged in one voxel blur edges and alter HU; reduce with thinner slices.", "Motion: blur, streaks or double edges; reduce with immobilization, breath-hold instructions, faster rotation and ECG gating.", "Metal: bright and dark streaks; remove external metal, use metal artifact reduction software, higher kVp or high-keV monoenergetic images, and angle around fillings when possible.", "Out-of-field: anatomy outside the SFOV causes streaks and shading; center the patient, raise arms, use a larger SFOV.", "Edge gradient: streaks from sharp high-contrast edges; reduced with thinner slices.", "Photon starvation through the shoulders or hips causes noisy streaks; tube current modulation and adaptive filtering help." ], "memory_tip": null, "board_traps": [ "Cupping is beam hardening, not a ring artifact.", "Thin slices reduce partial volume but do not fix motion." ], "key_numbers": [] }, { "subcategory": "Image Evaluation and Archiving", "title": "Equipment artifacts", "must_know": [ "Rings: a miscalibrated or failed detector element in third-generation scanners; fix with recalibration (air cal) or service.", "Streaks can come from a failed detector, data transfer errors or tube problems as well as patient factors.", "Tube arcing (high-voltage discharge in the tube) causes streaks and can signal an aging tube needing service.", "Cone-beam artifact: divergent rays in wide multidetector beams cause streaks or windmill patterns, worse at the z-axis edges; cone-beam reconstruction algorithms reduce it.", "Stair-step artifact on MPR/3D comes from thick slices or wide reconstruction intervals; use thin, overlapping reconstructions." ], "memory_tip": "Ring = one bad detector Rings round the center.", "board_traps": [ "A ring artifact is not patient motion.", "Stair-step is a reconstruction choice problem more than a hardware failure." ], "key_numbers": [] }, { "subcategory": "Image Evaluation and Archiving", "title": "Informatics, security and downtime", "must_know": [ "HIS manages hospital-wide data (admission, billing); RIS manages radiology scheduling, tracking and reports; EMR is one organization's chart, EHR is shareable across organizations.", "PACS stores and distributes images; DICOM is the standard for medical image format and transfer; HL7 is the standard for text data between HIS and RIS.", "DICOM modality worklist pulls demographics into the scanner and reduces patient ID errors; dose information can be sent as a DICOM radiation dose structured report.", "HIPAA protects patient health information: log off, use strong passwords, encrypt or secure removable media, share only the minimum necessary.", "Teleradiology sends images for remote interpretation, including third-party after-hours coverage.", "Downtime: register manually with careful identifiers, store images on the scanner, then send and reconcile with RIS/PACS when systems return." ], "memory_tip": "DICOM = pictures; HL7 = words.", "board_traps": [ "HL7 does not carry the images.", "Manual entry during downtime is a major source of mismatched studies; double-check identifiers." ], "key_numbers": [] } ] }, { "id": "procedures", "category": "Procedures", "scored_questions": 71, "weight_pct": 43.0, "topics": [ { "subcategory": "Head, Spine, and Musculoskeletal", "title": "Routine head and brain", "must_know": [ "Noncontrast head CT is first-line for head trauma and acute stroke to exclude hemorrhage before tPA.", "Angling the scan plane parallel to the supraorbitomeatal line (or tilting the gantry) keeps the lenses out of the beam.", "Epidural hematoma: biconvex (lens shaped), usually arterial (middle meningeal artery), does not cross sutures.", "Subdural hematoma: crescent shaped, from torn bridging veins, crosses sutures but not the falx or tentorium.", "Subarachnoid hemorrhage fills sulci and basal cisterns, classically from a ruptured aneurysm; follow with CTA.", "Acute ischemic infarct is often not visible in the first hours; a hyperdense MCA sign indicates clot.", "CSF is made by the choroid plexus and flows lateral ventricles to foramen of Monro to third ventricle to cerebral aqueduct to fourth ventricle.", "Contrast-enhanced head CT is used for tumor, metastases, abscess and infection when MRI is not available." ], "memory_tip": "Epidural = Egg (lens) shape, artery; Subdural = Smile/crescent, veins.", "board_traps": [ "A normal early CT does not exclude ischemic stroke.", "Contrast is not given for an initial stroke or trauma head CT." ], "key_numbers": [ { "label": "Acute hemorrhage", "value": "about 50-80 HU" }, { "label": "Glasgow Coma Scale", "value": "3-15" } ] }, { "subcategory": "Head, Spine, and Musculoskeletal", "title": "Brain perfusion and neurovascular CTA/CTV", "must_know": [ "Stroke CTA covers from the aortic arch to the vertex, usually with bolus tracking in the aortic arch or ascending aorta.", "Circle of Willis: anterior communicating, anterior cerebral, internal carotid, posterior communicating and posterior cerebral arteries, joined to the basilar from the vertebral arteries.", "CT perfusion repeatedly scans the same brain volume (cine or shuttle) during a contrast bolus to produce maps of CBF, CBV, MTT and Tmax/TTP.", "Infarct core shows reduced CBF and reduced CBV; penumbra (salvageable tissue) shows prolonged MTT/Tmax with relatively preserved CBV.", "Central volume principle: MTT = CBV / CBF.", "Perfusion delivers high local dose; check dose notification values (overdose events with hair loss led to national dose-check standards).", "CT venography evaluates dural venous sinus thrombosis using a later delay than arterial CTA; a filling defect in the sinus (empty delta sign) suggests clot." ], "memory_tip": "Core is dead: CBV down. Penumbra is at risk: MTT up, CBV kept.", "board_traps": [ "Reduced CBF alone does not separate core from penumbra; CBV does.", "Perfusion dose is concentrated in one slab; the CTDIvol is high even though DLP looks modest." ], "key_numbers": [ { "label": "AAPM notification value, brain perfusion", "value": "CTDIvol 600 mGy" } ] }, { "subcategory": "Head, Spine, and Musculoskeletal", "title": "Temporal bones, orbits and sinuses", "must_know": [ "Temporal bone/IAC: very thin slices (about 0.5-0.6 mm), sharp bone kernel, small targeted DFOV for each side separately.", "Middle ear ossicles: malleus, incus, stapes; inner ear: cochlea, vestibule and semicircular canals; IAC carries cranial nerves VII and VIII.", "Orbits: thin axial slices with coronal reformats for fracture, foreign body and cellulitis; contrast for infection or mass.", "Orbital blowout fracture involves the orbital floor into the maxillary sinus (or medial wall into ethmoids); look for inferior rectus entrapment.", "Sinus CT is usually noncontrast; coronal images best show the ostiomeatal complex, the shared drainage path of the maxillary, frontal and anterior ethmoid sinuses.", "Air-fluid levels suggest acute sinusitis; image-guided sinus surgery uses dedicated thin-slice navigation protocols." ], "memory_tip": "Ossicles in order of sound: Malleus, Incus, Stapes (MIS).", "board_traps": [ "Acoustic schwannoma in the IAC is best shown with MRI; CT detail of bone is its strength.", "Sinus CT does not need IV contrast unless complications like orbital or intracranial spread are suspected." ], "key_numbers": [] }, { "subcategory": "Head, Spine, and Musculoskeletal", "title": "Maxillofacial bones, mandible and TMJ", "must_know": [ "Facial trauma CT uses thin bone-kernel slices with coronal/sagittal MPR and 3D volume rendering for surgical planning.", "Le Fort I = horizontal maxillary fracture (floating palate); Le Fort II = pyramidal; Le Fort III = craniofacial separation; all involve the pterygoid plates.", "Zygomaticomaxillary complex (tripod) fracture separates the zygoma at its attachments.", "Dedicated mandible/dental implant CT uses curved panoramic and cross-sectional reformats to map bone height and the inferior alveolar nerve canal.", "TMJ CT shows the bony condyle and fossa, often imaged closed- and open-mouth; MRI is needed for the articular disc.", "Align the scan plane to avoid dental amalgam streaks through the area of interest." ], "memory_tip": null, "board_traps": [ "TMJ disc displacement is an MRI question, not CT.", "The mandibular canal (inferior alveolar nerve) must be marked before implant placement." ], "key_numbers": [] }, { "subcategory": "Head, Spine, and Musculoskeletal", "title": "Spine and postmyelogram", "must_know": [ "Cervical spine trauma CT runs from skull base through at least T1 with thin bone-kernel axial images and sagittal and coronal reformats.", "Cervical vertebrae have transverse foramina that carry the vertebral arteries; thoracic vertebrae have rib facets; lumbar bodies are largest.", "Jefferson = C1 burst fracture; hangman = bilateral C2 pars/pedicle fracture; dens fractures involve C2 odontoid; Chance = horizontal flexion-distraction fracture (lap belt) at the thoracolumbar junction.", "Spondylolysis is a pars interarticularis defect; spondylolisthesis is forward slip of one vertebra on another.", "The spinal cord ends at the conus medullaris around L1-L2; below it is the cauda equina.", "Postmyelogram CT follows intrathecal contrast by lumbar puncture, typically within a few hours; roll the patient to mix contrast before scanning. It shows cord compression and nerve root sleeves when MRI is contraindicated.", "Lumbar spine: supine with knees flexed (support under knees) reduces lordosis." ], "memory_tip": "Jefferson = C1 (first), Hangman = C2.", "board_traps": [ "MRI, not CT, is preferred for disc and cord detail when the patient can have it.", "Scanning a postmyelogram patient without mixing gives layered contrast and poor root filling." ], "key_numbers": [ { "label": "Conus medullaris", "value": "about L1-L2" } ] }, { "subcategory": "Head, Spine, and Musculoskeletal", "title": "Musculoskeletal, arthrography and runoff", "must_know": [ "Extremity CT evaluates complex fractures (tibial plateau, calcaneus, acetabulum, distal radius, scaphoid) and surgical planning with MPR and 3D.", "Place the extremity of interest at isocenter and move the other limb out of the field; for upper extremity, raise the arm overhead (swimmer/superman position) when possible to avoid torso streaks.", "Post-arthrogram CT: contrast injected into the joint under imaging guidance, then CT soon after to show labrum, cartilage and loose bodies, especially when MRI is contraindicated.", "Shoulder: Hill-Sachs lesion is a posterolateral humeral head impaction and Bankart is an anteroinferior glenoid injury, both from anterior dislocation.", "Bony pelvis/hip: CT with 3D maps acetabular and femoral neck fractures and sacroiliac joints.", "CTA runoff: aorta to feet with bolus tracking in the abdominal aorta; match table speed to contrast flow so the scan does not outrun the bolus, and add a delayed pass if distal vessels are not opacified." ], "memory_tip": null, "board_traps": [ "Running a runoff at maximum table speed can outrun the bolus and mimic occlusion in the calves.", "Keeping both arms down for a wrist study puts the torso in the beam and adds artifact and dose." ], "key_numbers": [] }, { "subcategory": "Head, Spine, and Musculoskeletal", "title": "Patient factors and interventional procedures", "must_know": [ "Pediatric: size-based protocols, immobilization, feed-and-wrap for infants, sedation per policy, and smaller IV gauge with lower flow rates.", "Geriatric: fall risk, reduced renal function, hearing and mobility limits; give clear instructions and extra positioning support.", "Bariatric: check table weight limit and bore size; raise kVp/mAs, use larger SFOV, and expect more noise and out-of-field artifact.", "CT-guided biopsy and drainage: consent, coag labs, time-out, lidocaine, skin marker grid, needle confirmation images, and post-procedure images for complications.", "After lung biopsy the most common complication is pneumothorax; after any biopsy watch for bleeding.", "Trauma whole-body protocols prioritize speed: noncontrast head and cervical spine, then contrast chest, abdomen and pelvis." ], "memory_tip": null, "board_traps": [ "Exceeding the table weight limit risks equipment failure and inaccurate table motion; never exceed it.", "Aspiration and biopsy both need a time-out; small procedures are not exempt." ], "key_numbers": [] }, { "subcategory": "Neck and Chest", "title": "Larynx, airway and soft tissue neck", "must_know": [ "Soft tissue neck CT with IV contrast evaluates masses, abscess and lymph nodes, from skull base to aortic arch.", "Lower the shoulders as much as possible to reduce streaks; ask the patient not to swallow and to breathe quietly.", "Phonation (\"eee\") tests vocal cord motion; a modified Valsalva distends the pyriform sinuses and hypopharynx; puffed cheeks distend the oral cavity.", "Landmarks: hyoid about C3, thyroid cartilage about C4-C5, cricoid cartilage about C6 (larynx ends and trachea and esophagus begin); carotid bifurcation near the upper thyroid cartilage.", "The carotid sheath contains the common/internal carotid artery, internal jugular vein and vagus nerve.", "Normal thyroid is hyperdense on noncontrast CT because it stores iodine." ], "memory_tip": null, "board_traps": [ "Do not mistake normal hyperdense thyroid for hemorrhage or contrast.", "Swallowing during the scan blurs the larynx; give instructions before scanning." ], "key_numbers": [ { "label": "Hyoid", "value": "about C3" }, { "label": "Thyroid cartilage", "value": "about C4-C5" }, { "label": "Cricoid", "value": "about C6" } ] }, { "subcategory": "Neck and Chest", "title": "Mediastinum, aorta and routine chest", "must_know": [ "Routine chest: arms above head, deep inspiration breath-hold, scan from lung apices through the adrenals for cancer staging.", "Aortic arch branches in order: brachiocephalic (innominate), left common carotid, left subclavian.", "The carina sits about T4-T5 (sternal angle); the thymus is in the anterior mediastinum.", "Anterior mediastinal masses: thymoma, teratoma, thyroid, lymphoma.", "Aortic dissection: noncontrast series to detect intramural hematoma, then CTA; ECG gating reduces aortic root motion. Stanford A involves the ascending aorta (surgical); B does not (usually medical).", "Right-arm injection avoids dense contrast in the left brachiocephalic vein, which crosses in front of the arch and causes streaks." ], "memory_tip": "Anterior mediastinum = the 4 Ts.", "board_traps": [ "The left brachiocephalic vein is not an arch branch; arteries come from the arch, veins drain to the SVC.", "Skipping the noncontrast series in suspected dissection can miss intramural hematoma." ], "key_numbers": [ { "label": "Carina", "value": "about T4-T5" } ] }, { "subcategory": "Neck and Chest", "title": "Pulmonary embolism CTA", "must_know": [ "PE CTA uses bolus tracking with the ROI in the main pulmonary artery and a high flow rate (about 4-5 mL/s) with saline chaser.", "A PE appears as a filling defect in an opacified pulmonary artery; a saddle embolus straddles the main pulmonary artery bifurcation.", "Deep inspiration can draw unopacified IVC blood into the right heart (transient interruption of contrast); shallow breath-hold instructions help.", "Combined CT venography of the pelvis and legs, if ordered, uses a delayed acquisition to look for DVT.", "A negative D-dimer in a low-risk patient may avoid CTA altogether." ], "memory_tip": null, "board_traps": [ "Placing the tracking ROI in the aorta for a PE study triggers too late for pulmonary arteries.", "Poor opacification from transient interruption can mimic or hide emboli." ], "key_numbers": [ { "label": "Typical PE flow rate", "value": "about 4-5 mL/s" } ] }, { "subcategory": "Neck and Chest", "title": "Lungs, HRCT and low-dose lung screening", "must_know": [ "Right lung has 3 lobes (horizontal and oblique fissures); left has 2 (oblique fissure), with the lingula in the left upper lobe.", "HRCT: thin slices (about 1 mm), sharp lung kernel, no IV contrast, inspiratory plus expiratory images for air trapping and prone images to tell dependent atelectasis from early interstitial disease.", "Interstitial lung disease findings include reticulation, ground-glass opacity, traction bronchiectasis and honeycombing (UIP pattern is basal and subpleural).", "Incidental lung nodules follow Fleischner Society guidelines; benign calcification patterns include diffuse, central, laminated and popcorn.", "USPSTF (2021) lung cancer screening: annual low-dose CT for ages 50-80 with at least 20 pack-years who smoke now or quit within 15 years; Medicare covers ages 50-77.", "Screening LDCT is noncontrast, low dose, and reported with ACR Lung-RADS categories.", "Pack-years = packs per day x years smoked." ], "memory_tip": "HRCT = thin, sharp, prone, expiration.", "board_traps": [ "Contrast is not used for HRCT or screening LDCT.", "Prone HRCT images are for dependent atelectasis, not for patient comfort." ], "key_numbers": [ { "label": "Screening age (USPSTF 2021)", "value": "50-80 years" }, { "label": "Smoking history", "value": ">= 20 pack-years" }, { "label": "Years since quitting", "value": "within 15 years" }, { "label": "ACR screening dose target, standard size", "value": "CTDIvol 3 mGy or less" } ] }, { "subcategory": "Neck and Chest", "title": "Cardiac CT: CCTA, calcium scoring, gating, TAVR", "must_know": [ "CCTA prep: target heart rate about 60-65 bpm or less (metoprolol), sublingual nitroglycerin, regular rhythm, practiced breath-hold.", "Prospective gating (step-and-shoot) exposes only during a chosen phase, commonly mid-diastole around 70-75% of the R-R interval; lowest dose, needs low regular heart rate.", "Retrospective gating scans helically at low pitch (about 0.2-0.4) with continuous exposure, so any phase can be reconstructed (function, valves); higher dose, reduced with ECG-based mA modulation.", "Coronary anatomy: left main splits into LAD and circumflex; RCA runs in the right AV groove; dominance is set by which artery supplies the posterior descending artery (right dominance is most common).", "Calcium scoring: noncontrast, prospectively gated, 3 mm slices at 120 kVp, Agatston method; a score of 0 means no detectable calcified plaque.", "TAVR planning: ECG-gated CTA of the aortic root and annulus plus CTA of chest, abdomen and pelvis to measure iliofemoral access vessels.", "Bolus tracking for CCTA is placed in the ascending (or descending) aorta." ], "memory_tip": "Pro = Pick one phase (low dose). Retro = Record everything (high dose, any phase).", "board_traps": [ "Retrospective gating is not the low-dose option.", "Calcium scoring uses no IV contrast." ], "key_numbers": [ { "label": "Target heart rate", "value": "<= 60-65 bpm" }, { "label": "Common diastolic phase", "value": "about 70-75% R-R" }, { "label": "Calcium score slice/kVp", "value": "3 mm, 120 kVp" }, { "label": "Retrospective pitch", "value": "about 0.2-0.4" } ] }, { "subcategory": "Neck and Chest", "title": "Airway, chest wall, esophagram and chest procedures", "must_know": [ "Airway CT uses thin slices with MinIP and virtual bronchoscopy; dynamic inspiratory/expiratory imaging assesses tracheomalacia.", "Chest wall CT evaluates rib and sternal fractures, masses and pectus excavatum (Haller index = transverse chest width / AP distance from sternum to spine).", "CT esophagram: oral water-soluble contrast given right before scanning to detect esophageal leak or perforation (e.g., Boerhaave, post-op anastomosis); avoid barium when perforation is suspected.", "CT-guided lung biopsy: post-procedure images for pneumothorax; placing the patient biopsy side down afterward is commonly used to reduce air leak.", "Thoracentesis drains pleural fluid; empyema may need CT-guided chest tube placement." ], "memory_tip": null, "board_traps": [ "Barium leaking into the mediastinum causes inflammation; use water-soluble agents first for suspected perforation.", "MinIP, not MIP, highlights the airway." ], "key_numbers": [ { "label": "Haller index suggesting surgical candidacy", "value": "> 3.25" } ] }, { "subcategory": "Abdomen and Pelvis", "title": "Multiphase liver and spleen", "must_know": [ "Liver has dual blood supply: portal vein about 75%, hepatic artery about 25%; the portal vein forms behind the pancreatic neck from SMV and splenic vein.", "Late arterial phase (about 35-40 s) shows hypervascular lesions: HCC, FNH, adenoma and hypervascular metastases (neuroendocrine, renal cell, thyroid, melanoma).", "Portal venous phase (about 60-70 s) is the routine abdominal phase and best for hypovascular metastases such as colon cancer.", "Delayed phase (about 3-5 min) shows HCC washout and capsule and fill-in of hemangioma, which enhances peripherally and nodularly, filling in toward the center.", "Noncontrast liver lower in HU than spleen suggests fatty liver.", "The spleen enhances heterogeneously (striped) in the arterial phase as a normal finding; judge it in the portal venous phase. Splenic injury is common in blunt trauma." ], "memory_tip": "Arterial = bright hypervascular; Portal = dark hypovascular; Delayed = washout and fill-in.", "board_traps": [ "Arterial-phase splenic heterogeneity is not a laceration.", "Most liver metastases are hypovascular and best seen in portal venous phase, not arterial." ], "key_numbers": [ { "label": "Late arterial", "value": "about 35-40 s" }, { "label": "Portal venous", "value": "about 60-70 s" }, { "label": "Delayed/equilibrium", "value": "about 3-5 min" } ] }, { "subcategory": "Abdomen and Pelvis", "title": "Multiphase pancreas", "must_know": [ "Pancreatic protocol: pancreatic parenchymal (late arterial) phase about 40-50 s for maximum contrast between enhancing gland and hypoenhancing adenocarcinoma, plus portal venous phase for liver metastases and veins.", "Thin slices with MPR/CPR assess resectability: tumor contact with the SMA, celiac axis, common hepatic artery, SMV and portal vein.", "Water as neutral oral contrast distends the duodenum and stomach without obscuring the gland or vessels.", "Neuroendocrine (islet cell) tumors are hypervascular and brightest in the arterial phase.", "Anatomy: head sits in the duodenal C-loop, uncinate process lies behind the SMV, tail reaches the splenic hilum, and the splenic vein runs along the back of the gland; the CBD passes through the head.", "Acute pancreatitis: elevated lipase/amylase; necrosis is best judged on contrast CT after the first few days (about 72 h)." ], "memory_tip": null, "board_traps": [ "Positive oral contrast can obscure the pancreatic head and duodenal wall on a pancreas protocol.", "Pancreatic adenocarcinoma is hypoenhancing, not hypervascular." ], "key_numbers": [ { "label": "Pancreatic phase", "value": "about 40-50 s" } ] }, { "subcategory": "Abdomen and Pelvis", "title": "Adrenals and kidneys", "must_know": [ "Adrenal protocol: noncontrast, portal venous (about 60-75 s) and 15-minute delay; noncontrast 10 HU or less suggests lipid-rich adenoma.", "Adenomas wash out quickly: absolute washout of 60% or more or relative washout of 40% or more.", "Renal phases: corticomedullary (about 25-40 s) shows arteries and cortex; nephrographic (about 80-120 s) gives homogeneous parenchyma and is best for detecting masses; excretory (about 5-15 min) opacifies collecting systems and ureters.", "A renal mass enhancing more than 20 HU is considered enhancing (solid); cystic masses are graded with the Bosniak classification.", "The right kidney usually sits slightly lower than the left because of the liver; kidneys, adrenals and ureters are retroperitoneal." ], "memory_tip": "Adrenal washout: 60 absolute, 40 relative.", "board_traps": [ "Small renal masses can be missed in the corticomedullary phase; the nephrographic phase is best for detection.", "Washout formulas need the noncontrast value for absolute washout; relative washout does not." ], "key_numbers": [ { "label": "Absolute washout", "value": "(enhanced - delayed) / (enhanced - unenhanced) x 100, adenoma >= 60%" }, { "label": "Relative washout", "value": "(enhanced - delayed) / enhanced x 100, adenoma >= 40%" }, { "label": "Adrenal delay", "value": "15 min" }, { "label": "Nephrographic phase", "value": "about 80-120 s" } ] }, { "subcategory": "Abdomen and Pelvis", "title": "Urogram, renal stone and bladder studies", "must_know": [ "Renal stone CT: noncontrast, low dose, kidneys through bladder; prone scanning separates a stone at the ureterovesical junction from one already in the bladder.", "Nearly all stones are visible on CT; dual energy can identify uric acid stones, which may be dissolved medically.", "CT urography for hematuria: noncontrast, nephrographic and excretory phases; split-bolus technique combines nephrographic and excretory in one acquisition for lower dose. Hydration helps distend the ureters.", "Dedicated delayed bladder imaging uses the excretory phase with a distended bladder to show filling defects.", "Retrograde CT cystogram for suspected bladder rupture: fill by gravity through a Foley with dilute iodinated contrast (commonly at least about 300 mL or to tolerance); clamped-catheter filling during the excretory phase is not adequate.", "Extraperitoneal rupture is most common and linked to pelvic fracture; intraperitoneal rupture (bladder dome) outlines bowel loops and usually needs surgery.", "Suspected urethral injury (blood at the meatus) needs a retrograde urethrogram before Foley placement." ], "memory_tip": null, "board_traps": [ "IV contrast hides stones in the collecting system; stone studies are noncontrast.", "Excretory-phase passive filling cannot exclude bladder rupture." ], "key_numbers": [ { "label": "CT cystogram fill volume (typical)", "value": "about 300-400 mL, to tolerance" } ] }, { "subcategory": "Abdomen and Pelvis", "title": "GI tract: enterography, appendicitis, obstruction and bleeding", "must_know": [ "Appendicitis: CT with IV contrast; findings are a dilated appendix (over about 6 mm), periappendiceal fat stranding and appendicolith; the appendix arises from the cecum.", "CT enterography: large-volume neutral oral contrast over about 45-60 minutes, enteric phase near 45-50 s, to show mural hyperenhancement in Crohn disease (often terminal ileum).", "Positive oral contrast (dilute barium or iodinated) opacifies bowel to separate loops from abscess or nodes; start well before scanning (about 60-90 min) to reach the colon.", "Bowel obstruction: look for a transition point; positive oral contrast is often unnecessary.", "GI bleeding CTA: noncontrast, arterial and portal venous phases with no positive oral contrast, which would hide active extravasation.", "Vascular landmarks: celiac trunk about T12, SMA about L1, renal arteries about L1-L2, IMA about L3, aortic bifurcation about L4." ], "memory_tip": null, "board_traps": [ "Positive oral contrast is wrong for GI bleed CTA and enterography.", "Free air with suspected perforation calls for water-soluble, not barium, oral contrast." ], "key_numbers": [ { "label": "Aortic bifurcation", "value": "about L4" }, { "label": "Abnormal appendix diameter", "value": "> about 6 mm" } ] }, { "subcategory": "Abdomen and Pelvis", "title": "Colorectal contrast and CT colonography", "must_know": [ "Rectal water-soluble contrast evaluates anastomotic leaks, fistulas and penetrating trauma near the rectosigmoid.", "CT colonography prep: bowel cleansing plus oral fecal/fluid tagging agent; distend the colon with CO2 (automated insufflator preferred) or room air through a small rectal catheter.", "Scan supine and prone (or decubitus) to shift fluid and stool and improve distension; low-dose, usually without IV contrast.", "Review with 2D images and 3D endoluminal fly-through; polyps of 6 mm or more are reported.", "Avoid colonography in acute colitis, acute diverticulitis or recent colonic surgery/biopsy because of perforation risk." ], "memory_tip": "Colonography: Clean, Tag, Inflate, Flip (supine and prone).", "board_traps": [ "A single position is not enough; residual fluid hides polyps.", "CO2 is preferred over room air because it absorbs faster and causes less cramping." ], "key_numbers": [ { "label": "Reportable polyp size", "value": ">= 6 mm" } ] }, { "subcategory": "Abdomen and Pelvis", "title": "Reproductive organs, abdominal vascular, trauma and interventions", "must_know": [ "Pelvic organs (uterus, ovaries, prostate, seminal vesicles) are best characterized by ultrasound or MRI; CT finds masses, abscesses and complications.", "Abdominal aortic aneurysm is an aortic diameter of 3 cm or more; EVAR follow-up CTA looks for endoleak (type II, from branch vessels, is most common).", "Abdominal trauma CT: portal venous phase for organ lacerations; active extravasation is contrast that changes shape or grows on delayed images.", "Morison's pouch (hepatorenal recess) is the most dependent upper abdominal space when supine; the rectouterine pouch (of Douglas) is the most dependent in the female pelvis.", "Retroperitoneal organs include adrenals, kidneys, ureters, aorta and IVC, most of the duodenum, pancreas (except tail), ascending and descending colon and rectum.", "CT-guided drainage places a pigtail catheter in abscesses; paracentesis removes ascites; aspiration samples fluid collections or cysts." ], "memory_tip": "Retroperitoneal = SAD PUCKER: Suprarenal glands, Aorta/IVC, Duodenum, Pancreas, Ureters, Colon (ascending/descending), Kidneys, Esophagus, Rectum.", "board_traps": [ "The spleen and liver are intraperitoneal; do not list them as retroperitoneal.", "Active extravasation grows on delayed images; a pseudoaneurysm keeps the same shape and follows blood pool." ], "key_numbers": [ { "label": "AAA threshold", "value": ">= 3 cm" } ] } ] } ], "last_minute_review": [ "ACR high-risk renal threshold for IV contrast: eGFR below 30 or any AKI.", "Metformin: hold 48 h after contrast only with AKI or eGFR below 30.", "Epinephrine 0.3 mg IM (1 mg/mL) is first-line for severe allergic-like reactions.", "Hypotension + bradycardia = vasovagal (legs up, fluids, atropine); hypotension + tachycardia = anaphylactoid (epinephrine, fluids).", "13-hour premedication: prednisone 50 mg at 13, 7, 1 h plus diphenhydramine 50 mg at 1 h.", "Power injection at 4-5 mL/s needs an 18-20 gauge antecubital IV; only power-rated central lines and ports.", "Breastfeeding need not be interrupted after iodinated contrast (ACR).", "Never inject an agent not labeled for intrathecal use into the thecal sac.", "Pitch = table feed per rotation / total beam collimation; >1 lowers dose at constant mA.", "Noise is proportional to 1/sqrt(mAs): quadruple mAs to halve noise.", "CTDIvol = CTDIw / pitch; DLP = CTDIvol x scan length; effective dose about DLP x k.", "CTDIvol is not patient dose; SSDE corrects for patient size.", "Photoelectric effect = contrast and patient dose (Z cubed); Compton = scatter and staff dose.", "Higher GE noise index lowers dose; center the patient at isocenter for correct mA modulation.", "Raw data allow new kernel, thickness, interval and DFOV; image data allow only windowing and reformats.", "Sharp kernel = detail and noise; smooth kernel = low noise and contrast resolution.", "Overlapping reconstructions improve MPR/3D without added dose.", "Pixel size = DFOV / matrix; window range = WL +/- WW/2.", "Air -1000, fat about -100, water 0, soft tissue about +40, acute blood about +50 to +80 HU.", "Rings = bad detector element; cupping and dark streaks between dense bone = beam hardening.", "Daily QC: water CT number near 0 HU, noise, uniformity, artifacts; DICOM moves images, HL7 moves text.", "Epidural = biconvex, arterial, does not cross sutures; subdural = crescent, venous, crosses sutures.", "Perfusion core: CBV down; penumbra: MTT/Tmax up with CBV preserved.", "Liver phases: late arterial 35-40 s, portal venous 60-70 s, delayed 3-5 min.", "Pancreatic phase about 40-50 s with water as neutral oral contrast.", "Adrenal adenoma: noncontrast 10 HU or less, absolute washout 60% or more, relative 40% or more at 15 min.", "Renal stone CT is noncontrast and low dose; prone separates UVJ stone from a bladder stone.", "Bladder rupture needs a retrograde CT cystogram; passive excretory filling is not enough.", "No positive oral contrast for GI bleed CTA or enterography.", "Lung screening (USPSTF 2021): ages 50-80, 20 pack-years, current smoker or quit within 15 years, annual LDCT without contrast." ] }