Quiz 1 Practice Questions

Question 1

how does Tr influence T1 weighting?

Answer 1

Tr controls the amount of Mii recovery, which indicates the extent to which fat and water have recovered along Bo and T1 weighting depends on Mii

Question 2

Specifiy whether the Te should be short or long in T2-weighted scans and why

Answer 2

long, to allow decay of M(perpendicular) due to fat

Question 3

What Tr and Te values should be used to acquire a conventional PD scan? (short or long)

Answer 3

long Tr, short Te

Question 4

Why can T2* weighting occur in MRI scans?

Answer 4

Bo field inhomogeneities cause spins to precess at different frequencies within scanner

Question 5

What does _ stand for in a SE scan and what is the relationship between it and the scan’s Te?

Answer 5

__ = time it takes to dephase spins after pi/2 pulse; Te = 2_

Question 6

What are the main reasons SE sequences are used?

Answer 6

they account for Bo inhomogeneities and preserve signal strength before readout

Question 7

What Tr and Te should be used to acquire a SE T2-weighted scan? (short or long)

Answer 7

long Tr, long Te

Question 8

Why can the Tr be shorter in GE sequences than in SE sequences?

Answer 8

gradient applications take shorter time than the time needed to dephase/rephase spins

Question 9

What Te should be used in GE sequences to minimize T2* effects and why?

Answer 9

short, so that neither water nor fat have had enough time to decay

Question 10

Why does a small flip angle minimize T1 weighting in GE scans?

Answer 10

(large) flip angles maximize fat signal, and thus T1 weighting