Physics · MRI subtopic

MRI Physics & Safety

MRI is the physics subtopic most likely to surprise you on the Core Exam — not because it's hardest, but because it's everywhere. Sequences, contrast mechanisms, k-space, artifacts, and safety all show up. This page is a single-session-friendly deep-dive: drill 20 MCQs, 20 flashcards, 3 image cases, and 3 interactive simulations.

Subtopics covered

Basic MR physicsLarmor frequency, net magnetization, RF excitation, T1/T2 relaxation, spin-echo refocusing.

Pulse sequencesSpin echo vs gradient echo, STIR, FLAIR, EPI. When each is indicated and why.

Contrast weightingT1w, T2w, PDw, DWI/ADC. TR/TE selection. Diffusion interpretation (true restriction vs T2 shine-through).

k-spaceCenter = contrast, periphery = edges. Parallel imaging (SENSE, GRAPPA) and the √R SNR penalty.

ArtifactsChemical shift (frequency direction), motion ghosting (phase direction), susceptibility blooming on GRE/SWI.

MR safetyACR zones I–IV, MR Conditional devices, SAR and RF heating, gadolinium/NSF, pregnancy.

Drill it Each loop is independent — do one or do all

MCQ Bank · 20

ABR-style questions across all six subtopics. Wrong answers explain each distractor and link to curated reading.

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Flashcards · 20

Larmor math, sequence parameters, artifact directions, safety zone rules — the facts that lock in the MCQs.

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Artifact Cases · 3

Chemical shift at the kidney-fat interface, motion ghosting on abdominal MRI, cerebral microbleeds with susceptibility blooming.

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Domain Mock

Physics-only timed mock, 40 questions. Calibrate your pace before exam day.

Interactive simulations Learn by touching the knobs

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TR / TE Explorer

Drag TR and TE sliders. Watch tissue contrast switch from T1w to T2w to PDw in real time.

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k-space Visualizer

Mask out the center vs the periphery of k-space. See how each region contributes to the reconstructed image.

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MR Safety Zones

Click through a floor plan of Zones I–IV. Screen props (pacemaker, wheelchair, oxygen tank) and see what goes where.

Curated reading Primary sources cited in the rationales

Radiopaedia — MRI (overview) Free, CC-licensed, constantly updated. Start here for any unfamiliar MRI concept.

Allen D. Elster — MRI Questions and Answers The canonical deep-dive physics resource. Every MRI physics question you've ever had is probably answered here.

Bushberg et al — Essential Physics of Medical Imaging The textbook every ABR physics question is written against. Chapters 12–13 cover MRI in detail.

ACR — MR Safety resources Authoritative source for zone definitions, screening, and conditional device policies.

Study tip: MCQ first, then review misses, then flashcards to cement, then cases to apply. The engine tracks your misses in localStorage and will surface a "yesterday's misses" warm-up the next time you open this page. Clearing browser storage resets it.