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Flashcards in Sequence Parameters & Options Deck (240)
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1

What is the difference in SNR between 2 adjacent pixels (eye's ability to detect difference)

CNR

2

Which parameter has the greatest influence on image quality

CNR

3

CNR is controlled by all the same factors as what

SNR

4

What is the ratio of signal amplitude to average noise amplitude called

SNR

5

Is signal predictable

yes

6

The induced voltage at the receiver coil is referred to as what

signal

7

Is noise predictible

no, it's random

8

What is noise dependent on

body habitus & electrical noise of the system

9

What parameter has the greatest influence on SNR

size of FOV

10

What is the ability of the imaging system to detect 2 points as separate

spatial resolution

11

Which pixel types give better spatial resolution: square or rectangular

square

12

What is the amount of tissue within a 3 D volume called

voxel volume

13

What determines voxel volume

FOV, matrix & slice thickness

14

What determines spatial resolution

voxel volume only

15

Formula for voxel volume

pixel phase x pixel frequency x slice thickness

16

What is the voxel volume when using a 24cm FOV, a 256x128 matrix & 3mm slices?

(240mm/256) x (240mm/128) x 3 = 5.27mm³

17

Which provide better spatial resolution - square or rectangular pixels

square

18

Which pixel type is better for reformatting 2D/3D images - square or rectangular

square

19

What is the amount of time it takes to fill k-space called

acquisition time

20

What has the greatest impact on the amount of patient motion detected on an image

acquisition time

21

What parameters affect acquisition time

TR, NSA/NEX, phase matrix, ETL & # of slices (during 3D only)

22

What is the formula to calculate 2D acquisition time for conventional sequences

TR x NSA x Phase encodings

(500ms x 1 x 256 = 128,000ms = 128sec = 2min 8 sec)

23

What is the formula to calculate 2D acquisition time for fast sequences

(TR x NSA x Phase encodings)/ETL

(500ms x 1 x 256)/4 = 32,000ms = 32sec

24

What is the formula to calculate 3D acquisition time for conventional sequences

TR x NSA x Phase encodings x slice #

(500ms x 1 x 256 x 24 = 3,072,000ms = 3,072sec = 51min 12sec)

25

List the 7 intrinsic parameters

T1 recovery
T2 decay
proton density
flow
ADC
perfusion
diffusion

26

List the 8 extrinsic parameters

TR
TE
flip angle
TI
ETL
b value
FOV
matrix

27

What are the 3 types of image contrast

T1
T2
PD

28

Which type of contrast appears as a difference in signal intensities between tissues with varying hydrogen proton concentrations

proton density contrast

29

What is the objective when trying to achieve T1 weighting

prevent recovery and decay

30

What is the objective when trying to achieve T2 weighting

allow recovery and decay