MRI MRI Sequences and Protocols 2

Question 1

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

Accepted Answer

DWI, fMRI, and perfusion imaging

Answer

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.

Question 2

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

Accepted Answer

Inflow enhancement: unsaturated blood entering a saturated imaging slab

Answer

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

Question 3

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

Accepted Answer

STIR (Short TI Inversion Recovery)

Answer

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

Question 4

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

Accepted Answer

Velocity and flow of fluids such as blood and CSF

Answer

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

Question 5

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

Accepted Answer

MR arthrography with intra-articular gadolinium dilution

Answer

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

MRI - Magnetic Resonance Imaging Practice Test

MRI - Magnetic Resonance Imaging Practice Test

MRI MRI Sequences and Protocols 2