Imaging parameters

Question 1

The difference in SNR between 2 adjacent pixels

Answer 1

Contrast to noise ratio (CNR)

Question 2

CNR and SNR are controlled by the _______ parameters in the ________ way.

Answer 2

Same/Same

Question 3

What parameter influences SNR the greatest?

Answer 3

FOV

Question 4

The ability of the imaging system to detect two points in a pixel as separate structures (distinguish)

Answer 4

Spatial Resolution

Question 5

Square pixels provide ________ resolution than rectangular pixels

Answer 5

Better

Question 6

Which techniques providers square pixels?

Answer 6

Square FOV and a square matrix

Rectangular FOV and a rectangular matrix

Question 7

What factor has an affect on 3D image acquisition time, but has no effect on 2D image acquisition time?

Answer 7

Slice numbers

Question 8

Conventional Pulse sequence acquisition time formula

Answer 8

TR x NEX(NSA) x Phase encodings = scan time

Question 9

Fast spin echo pulse sequence scan time formula

Answer 9

TR X NEX X Phase encodings / ETL =
Scan time

Question 10

Formula for scan time during 3D image acquisition

Answer 10

TR x NEX x Phase encodings x Slice#
= Scan time

Question 11

What parameter predominantly controls T2* weighting?

Answer 11

Echo time (long TR and Long TE)

Question 12

What is another name for T2* Decay

Answer 12

Susceptibility Decay

Question 13

T2* image weighting depends on

Answer 13

T2 decay, magnetic field inhomogeneities
T2 decay, T2 prime
Transverse relaxation, T2 prime

Question 14

The dephasing of precessing spins due to magnetic field inhomogeneities is referred to as

Answer 14

T2 prime

Question 15

What is the abbreviation for T2 prime

Answer 15

T2’

Question 16

What parameter is described as the time between the alpha pulse and the peak of the echo?

Answer 16

TE (echo time) - measured in milliseconds

Question 17

The time of inversion takes place between

Answer 17

The 180 degree inversion pulse and the excitation pulse during Inversion recovery sequences

Question 18

NSA/NEX determines how many times signal is encoded within each line of k-space by controling the amplitude and the slope of which gradient

Answer 18

Phase encoding gradient

Question 19

Flip angle is controlled by

Answer 19

The amplitude and duration of incoming RF pulse

Question 20

To obtain THIN slices a ___________ slice-select gradient slope and a ________ bandwidth is used

Answer 20

Steep/Narrow

Opposite for thick slices
Shallow/broad

Question 21

In order to reduce artifacts, it is recommended to use atleast a gap space of atleast _____% of the slice thickness

Answer 21

30%

Question 22

During FSE sequences, the echos that are closer to the effective TE value, get placed in the ________ of k-space as _________ data.

Answer 22

Center / Contrast

Question 23

During FSE sequences, the echos that are further from the effective TE value, get placed in the ________ of k-space as _________ data.

Answer 23

Periphery / Spatial Resolution

Question 24

Transmit bandwidth is selected by the system automatically when _________ is selected

Answer 24

Slice thickness

Question 25

If Receive bandwidth is doubled, approx. ______ of SNR is _______.

Answer 25

40% / Lost

Question 26

If Receive Bandwidth is halved, approx. _______ of SNR is ________.

Answer 26

40% / Gained

Question 27

What parameter directly controls the number of acquisitions performed within a pulse sequence

Answer 27

Concatenations

Question 28

Increasing concatenations usually allows the use of _______ TR if one is not obtainable due to the MRI’s system SAR limitations

Answer 28

Shorter