Chapter 3: Spin Echo

Question 1

Echo

Answer 1

when rephasing produces a signal

Question 2

2 ways to rephase the magnetic moment of hydrogen nuclei

Answer 2

• 180 RF pulse aka spin echo
• gradient aka gradient echo

Question 3

Spin echo (SE)

Answer 3

90 degree excitation to flip NVM fully into transverse plane
- induces voltage in the receiver coil

Question 4

FID occurs when

Answer 4

90 RF excitation pulse switches off

Question 5

T2*

Answer 5

dephasing from hommogeneities in B0 field

Question 6

tau

Answer 6

time between the RF excitation pulse and 180 RF rephasing pulse
- and then time between the 180 rephasing pulse and the echo

Question 7

Time inversion (TI)

Answer 7

time from 180 degree RF inverting pusle to the 90 degree Rf excitation pulse

Question 8

STIR

Answer 8

short tau inversion recovery
- suppresses fat

Question 9

FLAIR

Answer 9

fluid attenuated inversion recovery
- suppresses CSF/ liquid

Question 10

repetition time

Answer 10

time between each 90 degree RF pulse for each slice

Question 11

Echo time

Answer 11

time between each 90 degree RF pulse and the peak of the spin echo

Question 12

conventional spin echo

Answer 12

90 degree RF pulse followed by one or more 180 rephasing pulses to create one or more spin echoes

Question 13

spin echo

Answer 13

characterized by 180 rephasing pulses that refocus magnetic moment

Question 14

T1, T2, and PD weighting achieved by using

Answer 14

conventional spin echo
- still the gold standard to image anatomy and pathology

Question 15

FSE/TSE

Answer 15

SE sequences with much shorter scan times
- RARE- rapid acquisition with relaxation enhancement

Question 16

k-space

Answer 16

area in the array processor where the digital data on spatial frequency is stored

Question 17

matrix

Answer 17

number of pixels in the frequency and phase axis of the image

Question 18

pixel

Answer 18

2D location within slice

Question 19

voxel

Answer 19

3D cube within a tissue

Question 20

TI required to null the signal from tissue is

Answer 20

0.69 times the relaxation time

Question 21

No gadolinium in T1

Answer 21

nullifies the enhanced tissue

Question 22

J coupling

Answer 22

increase the T2 decay time of fat when multiple RF pulses are applied in TSE/FSE

Question 23

TR controls

Answer 23

amount of T1 recovery and T1 contrast

Question 24

TE controls

Answer 24

amount T2 decay and T2 contrast

Question 25

ETL/TE determines

Answer 25

number of K-0space lines filled every TR

Question 26

rephase

Answer 26

nuclei will come back into phase when Rf is applied

Question 27

dephasing

Answer 27

when there are differences in magnetic field (inhomogeneities) - some nuclei will speed up or slow down

Question 28

Pulse sequence CSE

Answer 28

T1 weighted TR- 300-700ms Te- 10-30ms Duel Echo TR- 2000+ TE1- 20ms TE2- 80ms

Question 29

effective TE

Answer 29

TE the operator wishes to weigh the image

Question 30

contrast difference between FSE and CSE

Answer 30

- fat remains bright on T2 images - muscle appears darker - reduction in magnetic susceptibility artifacts from metal implants

Question 31

T2 FSE

Answer 31

TR- 3000-10000ms effective TE- 80-140 ms ETL- 12-30

Question 32

SS-TS

Answer 32

all K-space are acquired at once

Question 33

inversion recovery

Answer 33

180 inverting pulse then 90 degree pulse follows then 180 rephasing pulse produces spin echo

Question 34

STIR parameters

Answer 34

TI- 150-175ms TE- 50ms TR- 4000ms ETL- 16-20ms

Question 35

STIR visualizes

Answer 35

musculoskeletal imaging - lesion and tumors seen clearly

Question 36

FLAIR parameters

Answer 36

TI- 1700-2000ms TE 70+ ms TR- 6000+ ms ETL- 16-20

Question 37

double IR

Answer 37

useful for morphoilogy of heart and great vessesl

Question 38

triple IR

Answer 38

useful for determining fatty infiltration of heart walls