Parameters and Tradeoffs

Question 1

SNR

Answer 1

signal to noise ratio

Question 2

The amount of voltage induced in the coil at the time the echo is collected

Answer 2

signal

Question 3

The frequencies of RF energy that exist randomly in time and space

Answer 3

noise

Question 4

Describe low SNR

Answer 4

grainy
noisy

Question 5

Coil position for maximum signal

Answer 5

transverse plane, perpendicular to B0

Question 6

The parameter controls the number of echos stored per line of k-space

Answer 6

number of signal averages (NSA or NEX)

Question 7

A range of frequencies

Answer 7

bandwidth

Question 8

The smallest unite of a digital image

Answer 8

pixel

Question 9

3D unit of volume

Answer 9

voxel

Question 10

Find voxel volume

Answer 10

pixel area x slice thickness

Question 11

Find pixel area

Answer 11

FOV/Matrix

Question 12

Name the 2 dimensions of the pixel

Answer 12

phase matrix
frequency matrix

Question 13

Which matrix will always be the smaller number?

Answer 13

phase matrix

Question 14

Scan Time equation

Answer 14

TR x Phase Matrix x NEX

Question 15

What’s known as under sampling and over sampling?

Answer 15

Rectangular FOV

Question 16

Does Rec FOV affect voxel size?

Answer 16

no, doesn’t change resolution

Question 17

What increases number of echoes but doesn’t add any dimension to the image?

Answer 17

oversampling

Question 18

Oversampling Benefits

Answer 18

avoid aliasing
increase SNR
increase scan time
no change to resolution

Question 19

TR increased

Answer 19

increase SNR
increase number of slices
increase scan time
decreases T1 weighting

Question 20

TR decreased

Answer 20

decrease scan time
decrease SNR
decrease number of slices
increase T1 weighting

Question 21

TE increased

Answer 21

decrease SNR
increase T2 weighting

Question 22

TE decreased

Answer 22

increase SNR
decrease T2-weighting

Question 23

NEX increased

Answer 23

increase SNR
increase in scan time
increase signal averaging

Question 24

NEX decreased

Answer 24

decrease SNR
decrease signal averaging
decrease in scan time

Question 25

Slice thickness increased

Answer 25

increases SNR increase coverage of anatomy increase partial voluming decrease spatial resolution

Question 26

Slice thickness decreased

Answer 26

increase spatial resolution decrease partial voluming decrease SNR decrease coverage

Question 27

FOV increased

Answer 27

increase SNR increase coverage of anatomy decrease potential of aliasing decrease spatial resolution

Question 28

Matrix increased

Answer 28

increase spatial resolution increase scan time decrease SNR if pixel small

Question 29

Matrix decreased

Answer 29

decrease scan time decrease spatial resolution increase SNR if pixel large

Question 30

Receive bandwidth increased

Answer 30

decrease in chemical shift decrease in min TE decrease SNR

Question 31

Receive bandwidth decreased

Answer 31

increase in SNR increase in chemical shift increase in min TE

Question 32

Find best spatial resolution?

Answer 32

smaller voxel size smallest FOV

Question 33

Find best SNR

Answer 33

increase voxel volume increase slice thickness increase NEX increase FOV increase TR decrease TE decrease coils decrease bandwidth decrease matrix

Question 34

What happens when B0 increases,

Answer 34

SNR increases

Question 35

How to change an image from low resolution to better resolution?

Answer 35

decrease FOV decrease slice thickness decrease matrix increase NEX

Question 36

Increased multi slice leads to:

Answer 36

increase scan time decrease T1 weighting

Question 37

Factors affecting SNR

Answer 37

TR TE flip Angle bandwidth proton Density voxel volume

Question 38

Find new SNR

Answer 38

original SNR x square root of new factor of increase

Question 39

Benefits of GRE

Answer 39

scan time

Question 40

Under sampling Benefits

Answer 40

decrease scan time decrease SNR aliasing

Question 41

If an image looks too fuzzy/blurry,

Answer 41

increase matrix decrease slice thickness decrease FOV

Question 42

Get better T1 contrast,

Answer 42

decrease TR