Chapter 5 Pulse Sequences

Question 1

What are the two types of spin echo

Answer 1

Conventional and fast spin echo

Question 2

What is repetition time

Answer 2

The time allowed to occur between excitation pulses how much regrowth has happened in the longitudinal plane. Controls T1 relaxation and milliseconds

Question 3

What is TE

Answer 3

It is echo time and it determines the amount of decay allowed to occur in the transverse plane before the signal is read out. Controls T2 relaxation

Question 4

What is spin echo characterized by?

Answer 4

90° RF pulse followed by one or more 180 RF pulse

Question 5

Short vs Long TR/TE for the following:
SE T1
SE T2
SE PD

Answer 5

Short TR and TE
Long TR and TE
Long TR and short TE

Question 6

What are two other names for fast spin echo and what are they primarily used for?

Answer 6

RARE and turbo spin echo

Mostly for PD and T2

Question 7

What is a fast spin echo

Answer 7

Uses a train of 180s with there own echoes with different TEs

Choose effective TE so shallow phase in code steps will be placed appropriately

Question 8

What happens if you have a long ETL

Answer 8

The less susceptible or sensitive artifacts will be demonstrated

Question 9

What is IR

Answer 9

Inversion recovery

It’s a variation of a spin echo but it starts with a 180° RF pulse

Question 10

What controls contrast from the 180 pulse to the 90° RF pulse in IR

Answer 10

The TI which is inversion time

Question 11

What is the scan time formula for a spin echo? FSE?

Answer 11

TR x PEs x NSA

TR x PEs x NSA all divided by ETL

ETL/target TE/effective TE

Question 12

What is inversion time

Answer 12

The time interval between the initial 180 pulse and the 90° pulse

Question 13

What is STIR and what does it do you best?

Answer 13

Short TI inversion recovery
Suppresses fat. 150 ms

Do in all areas of the body

PD and T2

Question 14

What is FLAIR and what is best used for?

Answer 14

Fluid attenuated inversion recovery

Suppresses fluid water CSF
Only done in the brain also T2 only

2500ms water crosses xy plane

Longer T1 and T2 times

Question 15

What is gradient echo and what are the other two names for it?

Answer 15

Field echo or gradient recalled
There are no 180° pulses
Less than a 90° for excitation pulse
Gradient reversal utilized to rephrase H protons
It is not SS
It does not compensate for local MF in homogeneity’s

Question 16

How is an echo produced in a gradient echo

Answer 16

With a reversal of a gradient

Question 17

What do gradient echo’s show best

Answer 17

Always do with MRA’s

Show bone blood air in metal best
Great for trauma patients and stroke patients

Question 18

What is isotropic voxel?

Answer 18

Equal dimensions and every plane

If not equal then called anisotropic

Question 19

What is flip angle

Answer 19

It is used with gradient echo’s
In conjunction with the TR to prevent saturation

The excitation pulse controls the contrast

Question 20

What are the best flip angles for T1, T2 an PD

Answer 20

T1 = 90°
T2 = 15
PD =45

Question 21

What happens to M when you flip an angle

Answer 21

Throws M into the xy plane

Question 22

What is effective TE

Answer 22

It is the average of the echo train

So if there are nine 180 pulses then the fifth one in the middle would be your target

Question 23

What is RARE

Answer 23

Rapid acquisition relaxation enhancement

Question 24

What are some susceptibility artifact’s

Answer 24

Metal iron blood calcium