MRI MRI Sequences and Protocols 2 — Questions and Answers
Question 1: Echo planar imaging (EPI) is used in which MRI techniques due to its extremely fast acquisition speed?
- Conventional T1 spin echo and MRCP
- DWI, fMRI, and perfusion imaging (Correct answer)
- MR arthrography and spectroscopy
- STIR and inversion recovery sequences
Correct 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.
Question 2: In MR angiography, time-of-flight (TOF) technique produces vascular signal by exploiting which physical principle?
- T1 shortening by gadolinium contrast
- Inflow enhancement: unsaturated blood entering a saturated imaging slab (Correct answer)
- T2 prolongation of blood
- Chemical shift between blood and surrounding fat
Correct 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.
Question 3: Which inversion recovery technique is used to suppress fat signal in musculoskeletal MRI?
- FLAIR
- STIR (Short TI Inversion Recovery) (Correct answer)
- MPRAGE
- VIBE
Correct 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.
Question 4: Phase contrast MRI (PC-MRI) is primarily used to measure:
- Tissue T1 values
- Velocity and flow of fluids such as blood and CSF (Correct answer)
- Chemical metabolite concentrations
- Myelin content
Correct 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.
Question 5: Which MRI protocol modification is used to evaluate the acetabular labrum of the hip with maximum sensitivity for tears?
- Standard T2 FSE without contrast
- MR arthrography with intra-articular gadolinium dilution (Correct answer)
- Diffusion-weighted imaging of the hip
- T1 fat-saturated without contrast
Correct 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.
Question 6: In cardiac MRI, which sequence is used to assess myocardial viability and detect scar tissue?
- True FISP cine imaging
- Late gadolinium enhancement (LGE) with inversion recovery (Correct answer)
- First-pass perfusion with adenosine stress
- Black-blood T2 STIR
Correct 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.
MRI MRI Sequences and Protocols 2
Echo planar imaging (EPI) is used in which MRI techniques due to its extremely fast acquisition speed?