Spin Echo (SE)

Question 1

Define a T1w SE pulse sequence (alpha, TE, TR)

Answer 1

alpha = 90 degrees
TE: TE ,much less than T2 (~5 ms)
TR: TR~T1 (~800 ms)

TE should be short to minimize T2 decay effects and the TR should be short to enhance the effects of T1 decay

Question 2

What is T1w?

Answer 2

Highlight T1 contrast
TR~T1, TE much less than T2

Shorten TE to minimize effects of T2
(a longer wait allows for better realignment and less transverse magnetic moment)

CSF appears darkest

Question 3

What is T2w?

Answer 3

Highlight T2 contrast
TE~T2

TR much larger than T1 to minimize effects of T1

CSF appears brightest

Question 4

Define a T2w SE pulse sequence (alpha, TE, TR)

Answer 4

alpha = 90 degrees
TE: TE~T2 (~100 ms)
TR: TR much larger than T1 (~3000 ms)

TE should be long to enhance T2 decay effects and the TR should be long to minimize the effects of T1 decay.

Question 5

What is Inverse Recovery (IR) pulse sequence used for?

Answer 5

T1w imaging, removal of background signals (like water)

-180 degree pulse before SE sequence
-TI = time from 180 pulse to 90 pulse

Ex. Short Tau Inversion Recovery (STIR): for fat, Fluid-Attenuated Inversion Recovery (FLAIR): for fluid

Question 6

What is PDw?

Answer 6

Proton density weighting
TR much larger than T1, TE much less than T2

less tissue contrast, CSF appears darkest