MRI Sequences and Protocols Flashcards

Echo planar imaging (EPI) is used in which MRI techniques due to its extremely fast acquisition speed?

Answer: DWI, fMRI, and perfusion imaging

EPI acquires an entire k-space in a single excitation, enabling the speed needed for diffusion-weighted imaging, fMRI BOLD imaging, and dynamic perfusion studies.

In MR angiography, time-of-flight (TOF) technique produces vascular signal by exploiting which physical principle?

Answer: Inflow enhancement: unsaturated blood entering a saturated imaging slab

TOF MRA relies on flow-related enhancement: flowing unsaturated blood entering a slice that has saturated stationary tissue appears bright relative to background.

Which inversion recovery technique is used to suppress fat signal in musculoskeletal MRI?

Answer: STIR (Short TI Inversion Recovery)

STIR uses a short inversion time timed to null the longitudinal magnetization of fat, suppressing fat signal uniformly regardless of field inhomogeneity.

Phase contrast MRI (PC-MRI) is primarily used to measure:

Answer: Velocity and flow of fluids such as blood and CSF

PC-MRI encodes velocity as phase shifts of moving spins, allowing quantitative measurement of blood flow velocity and volume, and CSF pulsation.

Which MRI protocol modification is used to evaluate the acetabular labrum of the hip with maximum sensitivity for tears?

Answer: MR arthrography with intra-articular gadolinium dilution

MR arthrography with intra-articular dilute gadolinium distends the joint capsule, separating the labrum from the femoral head and maximizing sensitivity for labral tears.

In cardiac MRI, which sequence is used to assess myocardial viability and detect scar tissue?

Answer: Late gadolinium enhancement (LGE) with inversion recovery

Late gadolinium enhancement (LGE) uses an inversion recovery sequence 10–15 minutes after GBCA injection; scarred myocardium retains gadolinium and appears bright against nulled normal myocardium.