CAMRT MRI Exam flashcards

32 cards. Read the term and the definition here. The deck at the top of this page is optional.

Larmor equation

The resonance frequency of a nucleus equals the gyromagnetic ratio times the magnetic field strength; for hydrogen at 1.5 T it is about 63.9 MHz.

Zone IV

The magnet room itself, where the static field is present; access is physically restricted and only MR-safe equipment and screened personnel may enter.

MR-Conditional

A device labeling that means safe only under specified conditions such as field strength, spatial gradient, SAR limit, and coil type, not under all conditions.

SAR

Specific absorption rate, the RF power absorbed per unit mass in watts per kilogram; whole-body average is limited to 4 W/kg over 6 minutes in normal mode.

Quench

Loss of superconductivity causing rapid helium boil-off and oxygen displacement; evacuate the magnet room, ventilate, and call the service engineer.

T1 weighting

Produced by a short TR and short TE; tissues with short T1 such as fat appear bright and fluid appears dark.

T2 weighting

Produced by a long TR and long TE; tissues with long T2 such as fluid appear bright.

Proton density

Produced by a long TR and short TE; contrast depends mainly on the number of protons per unit volume with little T1 or T2 effect.

FLAIR

Fluid-attenuated inversion recovery; an inversion pulse with a long TI nulls CSF signal so periventricular lesions stand out on a T2-weighted image.

STIR

Short tau inversion recovery; an inversion pulse with a short TI nulls fat signal and is robust to field inhomogeneity, useful at low field.

Chemical shift artifact

A bright and dark rim at fat-water interfaces along the frequency-encode direction, caused by the roughly 3.5 ppm frequency difference between fat and water protons.

Aliasing

Wrap-around of anatomy outside the FOV into the opposite side of the image in the phase-encode direction; corrected by larger FOV or oversampling.

Zipper artifact

A bright line across the image caused by RF interference entering the room through a shield breach or external RF source.

Susceptibility artifact

Local field distortion near metal or air-tissue interfaces; worse with gradient echo, longer TE, and higher field, and reduced with spin echo and shorter TE.

Gadolinium contrast

A paramagnetic agent that shortens T1 and T2; typical extracellular dose is 0.1 mmol/kg and the effect is greatest on T1-weighted images.

Nephrogenic systemic fibrosis

A fibrosing disorder associated with gadolinium exposure in patients with severe renal impairment, more common with linear agents.

Extravasation management

Stop the injection, elevate the limb, apply a cold compress, document the volume and site, and arrange follow-up.

Anaphylactoid reaction

A severe contrast reaction with urticaria, bronchospasm, or hypotension; stop the injection, call for help, give oxygen, and administer epinephrine per protocol.

Parallel imaging

Undersampling phase-encode lines and using coil sensitivity information to reconstruct; it reduces scan time and echo train length at the cost of SNR.

K-space center

The central lines of k-space carry contrast information, while the periphery carries spatial detail; the filling order affects contrast and motion sensitivity.

Echo-planar imaging

A fast technique that fills all k-space lines after a single excitation; used for diffusion and functional imaging but sensitive to susceptibility distortion.

Diffusion-weighted imaging

Uses strong bipolar gradients; the b-value sets diffusion weighting and the ADC map removes T2 shine-through to show restricted diffusion.

Conus medullaris level

In adults the spinal cord typically terminates at L1-L2; below that level the cauda equina nerve roots are seen in the thecal sac.

Couinaud segments

The liver is divided into eight segments based on portal and hepatic vein anatomy, used to localize lesions for surgical planning.

SBAR handoff

Situation, Background, Assessment, Recommendation; a structured format for communicating with the radiologist, nurse, or anesthesia team.

Closed-loop communication

The sender states the message, the receiver repeats it back, and the sender confirms, reducing errors in high-stress situations.

Just culture

A framework that distinguishes human error from at-risk and reckless behavior, encouraging reporting without blame for honest mistakes.

PDSA cycle

Plan-Do-Study-Act; a small-scale test of a change with measurement before wider adoption in quality improvement.

Peripheral nerve stimulation

Induced by rapidly changing gradient fields at high dB/dt; the system enforces limits to keep stimulation below threshold.

RF shield

A copper enclosure around the magnet room that prevents external RF interference from entering and causing zipper or noise artifacts.

SNR and NEX

Signal-to-noise ratio increases with the square root of the number of acquisitions, so quadrupling NEX doubles SNR at four times the scan time.

Two-identifier check

Patient identification uses two identifiers such as name and date of birth, checked against the requisition before every study.