PS 2

Question 1

a “single shot” or “snap shot” F/TSE sequence is when the ________ equals the ________.

Answer 1

when the ETL equals the PHASE ENCODING STEPS REQUIRED.

Question 2

What are the main differences between echo imaging (GRE) vs Spin Echo (SE)?

Answer 2

Short TR’s
Gradient-induced echoes
<90° Slice excitation pulses.

Question 3

What is the main characteristic of Inversion Recovery (IR) vs Spin Echo (SE)?

Answer 3

IR Starts with a 180°-90°-180° RF slice excitaion order.

Question 4

A tissue that is “saturated” will yield a high or low SNR?

Answer 4

Low SNR.

Question 5

What is Echo Spacing?

Answer 5

The time between each echo in the echo train

Question 6

What is the gradient used to generate an echo in a GRE?

Answer 6

Gx

Question 7

True or False:

IR is a pulse sequence used only for T1 weighting.

Answer 7

False.

Question 8

True or False:

Magnetic Susceptibility effects can both degrade & improve diagnostic imaging quality.

Answer 8

True

Question 9

In GRE, what is used to eliminate residual transverse magnetization?

Answer 9

“Spoiler” pulses.

Question 10

What is the signal characteristic of a tissue at the null point?

(high or low SNR?)

Answer 10

Low SNR

Question 11

The calculation for scan time in a F/TSE is the same as SE except for:

Answer 11

Dividing the result by the ETL.

Question 12

In a SE sequence, if 120 phase encoding steps are selected, the TR is repeated _______ times.

Answer 12

120

Question 13

The ability of a tissue to become magnetized is:

Answer 13

Magnetic Susceptibility

Question 14

STIR is an IR sequence used to produce __________

Answer 14

Robust fat suppression

Question 15

A parameter used in IR that is not used in SE is:

Answer 15

TI (inversion time)

Question 16

In IR, the first 180° slice excitation pulse places the LMZ into the:

Answer 16

-z axis

Question 17

What is an effective method for reducing echo spacing?

Answer 17

Decrease frequency encoding steps

increase the receive bandwidth

Question 18

Signal dephasing due to local inhomogeneities is referred to as what?

Answer 18

T2’ (prime)

Question 19

When the TR is shorter than a tissue’s T2 decay time, the “leftover” transverse magnetization of that tissue is referred to as what?

Answer 19

Residual Transverse Magnetization

Question 20

Another characteristic of IR is that it always requires a _________ than SE.

Answer 20

Longer TR

Question 21

Tissues become saturated due to _____ flip angles and very ______ TR’s.

Answer 21

High Flip angles
Very short TR’s

Question 22

What happens when there is a great variance of T2 Decay in the ETL?

Answer 22

F/TSE blurring

Question 23

What is the point at which the LMV crosses from the -z axis to the +z axis known as?

Answer 23

Null Point

Question 24

What is the best T1 time for STIR imaging at 1.5T

Answer 24

160 msec

Question 25

______ is described as the ability of a substance to attract iron, cobalt, and nickel.

Answer 25

Magnetism

Question 26

What is a pulse sequence?

Answer 26

a series of events that include radio frequency transmissions & detections & various magnetic gradient fields timed to achieve an image with a particular SNR, spatial resolution, and contrast.

Question 27

Gradient echos are ________ at correcting for dephasing caused by inhomogenities while 180° radio frequency echoes are _________.

Answer 27

ineffective effective.

Question 28

In IR, the time between the 180° & the first 90° RF pulse is called T1 as well as:

Answer 28

Tau

Question 29

In fast/turbo spin echo (F/TSE), if the echo train is 8 and the number of phase encoding selected is 256, what is the number of TR's that are repeated?

Answer 29

32

Question 30

In a T2W flair sequence of the brain, what is suppressed in order to make long T2 pathologies moer conspicuous? (such as edema, inflammation, and certain tumors)

Answer 30

CSF

Question 31

in Fast/turbo spin echo (F/TSE) , what is the echo train made up of?

Answer 31

a series of 180° RF Pulses

Question 32

In the IR pulse sequence known as a FLAIR, what is suppressed?

Answer 32

Fluid