{
"id": "mri-patient-care-safety",
"modality": "MRI",
"category": "Patient Care & Safety",
"title": "MRI Patient Care & Safety: Zones, Implants, SAR and Gadolinium",
"minutes": 9,
"slides": [
{
"id": 1,
"diagram": "title",
"heading": "MRI Patient Care & Safety",
"bullets": [
"37 of 200 scored questions (18.5%)",
"Patient Care 16 plus Safety 21",
"Zones, screening, fields, SAR, gadolinium, emergencies"
],
"narration": "Welcome to MRI Patient Care and Safety. Together these two categories are 37 of the 200 scored questions on the MRI boards, about 18 and a half percent. That is Patient Care with 16 questions plus Safety with 21. We'll cover the four safety zones, implant screening and labels, the three magnetic fields and how each one can hurt a patient, specific absorption rate, gadolinium dosing and kidney risk, and what to do in an emergency in the scanner room. Let's get started.",
"svg": ""
},
{
"id": 2,
"diagram": "mr-zones",
"heading": "The four MR safety zones",
"bullets": [
"Zone I: public access",
"Zone II: interface where patients are screened",
"Zone III: restricted, controlled by MR personnel",
"Zone IV: the magnet room itself",
"Level 2 personnel supervise all non-MR people"
],
"narration": "The American College of Radiology, or A C R, divides an MR suite into four zones that get closer to the magnet. Zone one is the public area anyone can walk into. Zone two is the interface where patients are screened and supervised. Zone three is restricted, and MR personnel control who gets in. Zone four is the magnet room itself. A favorite trap calls Zone three the magnet room, so don't fall for it. MR technologists are Level 2 MR personnel, and any patient, visitor or untrained staff member enters Zones three and four only after screening and under Level 2 supervision.",
"svg": ""
},
{
"id": 3,
"diagram": "mr-labels",
"heading": "Screening and MR labels",
"bullets": [
"Written form plus verbal interview, every patient",
"MR Safe: green square, no known hazard",
"MR Conditional: yellow triangle, only as labeled",
"MR Unsafe: red circle with a slash",
"Metal work or eye injury: clear the orbits first"
],
"narration": "Screening is your strongest safety tool. Every patient, and every person entering Zone four, gets a written form plus a verbal interview. Know the three labels. MR Safe is a green square with no known hazard in any MR environment. MR Conditional is a yellow triangle, safe only under the exact conditions on its label, such as field strength and heating limits, so a 1.5 tesla device is not cleared at 3 tesla. MR Unsafe is a red circle with a slash. And if a patient did metal work or had a metal eye injury, the orbits must be cleared, usually with radiographs, before scanning.",
"svg": ""
},
{
"id": 4,
"diagram": "static-field",
"heading": "Static field: always on",
"bullets": [
"Superconducting field stays on with power off",
"Pull is strongest near the bore entrance",
"Torque is strongest at isocenter",
"5 gauss line: pacemaker caution zone",
"FDA: 8 T adults, 4 T neonates"
],
"narration": "The static field, called B zero, is the projectile hazard, and a superconducting field stays on even when the power is off. Translational pull depends on how fast the field changes in space, so it is strongest near the bore entrance. Torque, the twisting force, is strongest at isocenter, where the field is highest. Think pull at the door, twist in the middle. The 5 gauss line, which is 0.5 millitesla, marks where the fringe field can affect pacemakers. And the FDA's static field limits are 8 tesla for adults, children and infants over one month, and 4 tesla for neonates.",
"svg": ""
},
{
"id": 5,
"diagram": "sar-limits",
"heading": "RF field: SAR and burns",
"bullets": [
"SAR is in watts per kilogram: enter true weight",
"Whole body: 2 W/kg Normal, 4 W/kg First Level",
"Head SAR limit: 3.2 W/kg",
"SAR rises with B0 squared: 3 T is about 4 times 1.5 T",
"Pad to break skin loops; never loop cables"
],
"narration": "The radiofrequency field heats tissue, and specific absorption rate, or SAR, measures it in watts per kilogram. SAR is calculated from the weight you enter, so enter the true weight. The whole-body limits are 2 watts per kilogram in Normal Operating Mode and 4 in First Level Controlled Mode, which needs medical supervision. The head limit is 3.2 watts per kilogram. SAR rises with the square of field strength, so 3 tesla deposits about four times the SAR of 1.5 tesla. To prevent burns, pad between skin surfaces and the bore, uncross ankles and hands, and never loop cables.",
"svg": ""
},
{
"id": 6,
"diagram": "gradient-safety",
"heading": "Gradients: noise and nerves",
"bullets": [
"Fast gradient switching (dB/dt) induces currents",
"Peripheral nerve stimulation: tingling or twitching",
"Gradients make the noise, loudest on EPI and DWI",
"Hearing protection for every patient, even sedated"
],
"narration": "The third field is the gradient field, which switches on and off very fast. That rate of change, written d B over d t, induces currents in tissue by Faraday's law. The result can be peripheral nerve stimulation, felt as tingling or twitching. The gradients also make the knocking noise, as the coils vibrate inside the main field, and it is loudest on fast sequences like echo planar imaging and diffusion. A classic trap blames the noise on radiofrequency, so remember it's the gradients. Every patient gets hearing protection, including sedated patients and infants.",
"svg": ""
},
{
"id": 7,
"diagram": "mr-emergency",
"heading": "Codes, cryogens and quench",
"bullets": [
"Code: start CPR, move the patient out of Zone IV",
"Crash cart and code team stay out of Zone IV",
"Liquid helium about 4 K, expands about 750 to 1",
"Quench signs: hiss, white cloud, oxygen alarm",
"Quench only for a pinned person or a fire"
],
"narration": "In a cardiac arrest, start CPR, call the code, and move the patient out of Zone four to a prepared area. The crash cart, defibrillator and code team stay out of Zone four. Superconducting magnets are cooled by liquid helium at about 4 kelvin, and it expands about 750 to 1 as a gas, which can displace oxygen. A quench sounds like a loud hiss or bang with a white cloud and an oxygen alarm, so evacuate everyone. Only quench on purpose when a person is pinned by a metal object, or for a fire. Never quench for a code.",
"svg": ""
},
{
"id": 8,
"diagram": "gad-dose",
"heading": "Gadolinium agents and dose",
"bullets": [
"Paramagnetic: shortens T1, so enhancement is bright",
"Standard dose: 0.1 mmol/kg for most agents",
"0.5 mmol/mL agents: 0.2 mL/kg",
"Gadobutrol is 1.0 mmol/mL: 0.1 mL/kg",
"Example: 80 kg times 0.1, divided by 0.5 = 16 mL"
],
"narration": "Gadolinium agents are paramagnetic. They shorten the T1 of nearby water, so enhancing tissue turns bright on T1-weighted images. The standard dose for most agents is 0.1 millimoles per kilogram. Most agents come at 0.5 millimoles per milliliter, which works out to 0.2 milliliters per kilogram. Gadobutrol is twice as concentrated, at 1.0 millimole per milliliter, so it's only 0.1 milliliters per kilogram. Don't double it. Here's the math: an 80 kilogram patient times 0.1, divided by 0.5, equals 16 milliliters.",
"svg": ""
},
{
"id": 9,
"diagram": "nsf-reactions",
"heading": "Kidneys, NSF and reactions",
"bullets": [
"NSF risk: eGFR under 30, acute kidney injury, dialysis",
"Highest with older linear Group I agents",
"Premed: prednisone 50 mg at 13, 7 and 1 hour",
"Anaphylaxis: epinephrine IM is first-line",
"Vasovagal: slow pulse; anaphylaxis: fast pulse"
],
"narration": "Nephrogenic systemic fibrosis, or NSF, is the kidney-related risk. It shows up with an estimated glomerular filtration rate under 30, with acute kidney injury, or on dialysis, and mostly after the older linear Group 1 agents. For a prior gadolinium reaction, the ACR oral premed is prednisone 50 milligrams at 13, 7 and 1 hour before, plus diphenhydramine 50 milligrams at 1 hour. For anaphylaxis, intramuscular epinephrine is first-line. And tell reactions apart by the pulse: vasovagal is low blood pressure with a slow pulse, anaphylaxis comes with a fast pulse.",
"svg": ""
},
{
"id": 10,
"diagram": "summary",
"heading": "Lock these in",
"bullets": [
"Zone IV is the magnet room",
"Pull peaks at the bore entrance; torque at isocenter",
"Whole-body SAR 2 W/kg Normal, 4 First Level; head 3.2",
"Code in the scanner: CPR and move out of Zone IV",
"Gd 0.1 mmol/kg; NSF risk at eGFR under 30"
],
"narration": "Let's lock it in. Zone four is the magnet room, not Zone three. Pull peaks at the bore entrance, and torque peaks at isocenter. Whole-body SAR is limited to 2 watts per kilogram in Normal Mode and 4 in First Level, and the head limit is 3.2. If a patient codes in the scanner, start CPR and get them out of Zone four. Never quench for a code. And gadolinium is dosed at 0.1 millimoles per kilogram, with NSF risk at an eGFR under 30. Now hit Practice this chapter and test yourself.",
"svg": ""
}
]
}