MRI MRI Sequences and Protocols

Question 1

In a spin echo (SE) sequence, increasing the repetition time (TR) while keeping TE short primarily results in:

Accepted Answer

Decreased T1 weighting (more proton density/T2-like contrast)

Answer

A long TR allows full T1 recovery of all tissues, reducing T1 contrast differences; combined with short TE, this produces proton density weighting.

Question 2

FLAIR (Fluid-Attenuated Inversion Recovery) suppresses which signal and is most useful for detecting:

Accepted Answer

CSF signal; periventricular and cortical lesions

Answer

FLAIR uses an inversion pulse timed to null CSF, making periventricular lesions and cortical pathology (MS plaques, subarachnoid hemorrhage) visible against suppressed fluid.

Question 3

Which MRI sequence is most commonly used for evaluating liver lesions using T2 contrast with heavy T2 weighting for the bile ducts?

Accepted Answer

MRCP (heavily T2-weighted 3D or thick-slab)

Answer

MRCP uses heavily T2-weighted sequences to make bile and pancreatic fluid appear bright, providing a non-invasive map of the biliary and pancreatic ductal system.

Question 4

Gradient echo (GRE) sequences differ from spin echo sequences primarily because GRE:

Accepted Answer

Uses a gradient reversal to form an echo, making it sensitive to magnetic susceptibility (T2*)

Answer

GRE uses gradient reversal without a 180° refocusing pulse, making it sensitive to susceptibility effects (T2*) and allowing faster acquisition.

Question 5

Which parameter directly controls the degree of T2 weighting in a spin echo sequence?

Accepted Answer

TE (echo time)

Answer

TE determines how long transverse magnetization decays before sampling; a longer TE allows more T2 decay, increasing T2 contrast.

MRI - Magnetic Resonance Imaging Practice Test

MRI - Magnetic Resonance Imaging Practice Test

MRI MRI Sequences and Protocols