FINAL STUDYGUIDES

Question 1

Which pulse sequence timing parameter combination will result in T1 weighted images when performing a spin echo pulse sequence?

Answer 1

short TR/short TE

Question 2

Which pulse sequence timing parameter combination will result in Spin Density weighted images when performing a spin echo pulse sequence?

Answer 2

long TR/short TE

Question 3

Which pulse sequence timing parameter combination will result in T2 weighted images when performing a spin echo pulse sequence?

Answer 3

long TR/long TE

Question 4

When is a tissue vector considered to be partially saturated?

Answer 4

when it flips >90 degrees but <180

Question 5

When is a tissue vector considered to be fully saturated?

Answer 5

when it reaches 180 degrees from equilibrium, it is positioned along the –z axis

Question 6

A technologist sets up a pulse sequence as follows: type of pulse sequence: fast spin echo, TR = 3500 ms, TE = 20ms, matrix 256x192, NSA 3. What is the resulting image weighting?

Answer 6

Proton density

Question 7

Explain the term homogeneity, as it applies to MRI.

Answer 7

Homogeneity is the even-ness or uniformity of the static field

Question 8

State the source of T2’ decay.

Answer 8

T2’ decay is caused by inhomogeneities (uneven-ness) of the static field

Question 9

Which imaging parameter(s) control(s) the amount of T1 weighting present in images obtained by performing a gradient echo pulse sequence?

Answer 9

Flip angle and TR

Question 10

Which imaging parameter(s) control(s) the amount of T2 weighting present in images obtained by performing a gradient echo pulse sequence?

Answer 10

TE

Question 11

Name the component of the MR system that induces parallel or anti-parallel alignment of the magnetic moments in a sample of tissue

Answer 11

the static magnetic field

Question 12

Which gradient is simultaneously activated each time that RF is transmitted?

Answer 12

slice select

Question 13

Which gradient is applied, as the slice select gradient, when obtaining coronal images of the brain?

Answer 13

the Y gradient

Question 14

When the MR system applies a greater current amplitude to the activated gradient coils, what is the impact on the slope of the gradient?

Answer 14

the slope becomes steeper

Question 15

What is the impact on the speed of precession along a gradient?

Answer 15

spins in the area where the magnetic field becomes stronger precess faster, spins in the area where the magnetic field becomes weaker precess slower

Question 16

What is the impact on the phase position of the spins along the gradient?

Answer 16

The slope of the PE gradient determines the amount of phase shift present in the image; steep gradient has large phase shift and shallow gradient has small phase shift

Question 17

What is the impact on the direction of the gradient when the polarity of the current in the gradient coils is changed by the MR system?

Answer 17

when the polarity of the current applied to the gradient coil switches, the direction of the magnetic field gradient also switches

Question 18

Name the 3 processes that make up spatial encoding.

Answer 18

Slice selection, phase encoding, frequency encoding

Question 19

What two things does the MR system adjust when the technologist selects a slice thickness value?

Answer 19

the transmitted bandwidth and the slope of the slice select gradient

Question 20

If a technologist makes an adjustment to the bandwidth parameter, which is being adjusted:

Answer 20

receive bandwidth

Question 21

What is another name for the frequency encoding gradient?

Answer 21

the readout gradient

Question 22

Along which axis is the phase encoding gradient typically applied?

Answer 22

the short axis of the patient’s anatomy

Question 23

In what area of k-space is contrast data stored?

Answer 23

the center

Question 24

In what area of k-space is spatial resolution data stored?

Answer 24

the periphery or the edges

Question 25

What determines how many lines of data will be acquired along the phase axis of k-space?

Answer 25

the phase matrix

Question 26

What determines whether a positive or negative line of data will be acquired and stored in k-space?

Answer 26

the polarity of the phase encoding gradient applied by the system

Question 27

What determines whether the data acquired will be mapped into the center or periphery of k-space?

Answer 27

the amplitude or steepness of the phase encoding gradient applied by the system

Question 28

Name 3 methods of acquiring data in k-space.

Answer 28

sequential, 2-D volumetric, 3-D volumetric

Question 29

What type of domain is k-space?

Answer 29

a spatial frequency domain

Question 30

Where is k-space physically located?

Answer 30

in the array processor

Question 31

What are the two axes of k-space?

Answer 31

phase and frequency

Question 32

What happens once k-space is filled?

Answer 32

the pulse sequence is complete

Question 33

What user-selected parameter determines how many data points will be acquired for each line of k-space?

Answer 33

the frequency matrix

Question 34

Signal is:

Answer 34

reproducible & occurs at the TE time

Question 35

Noise is:

Answer 35

random & fluctuating

Question 36

What is the impact of an increase of B0 on SNR?

Answer 36

SNR increases as B0 increases

Question 37

Name the 3 parameters that impact voxel volume and therefore in-plane resolution.

Answer 37

FOV, matrix, slice thickness

Question 38

Describe the relationship between voxel volume and SNR.

Answer 38

direct, as voxel volume increases, SNR increases and vice versa

Question 39

A technologist changes the Number of Signals Averaged (NSA) of the scan protocol from 1NSA to 4NSA. What is the impact (increase or decrease) & the quantity of the impact on SNR?

Answer 39

SNR increases, it doubles

Question 40

A technologist adjusts the receive bandwidth from +/-32kHz to +/- 16kHz. State the impact on SNR and minimum TE

Answer 40

SNR increases by 40%, minimum TE increases

Question 41

What impact will an increase in TR have on SNR?

Answer 41

increasing TR, increases SNR and vice versa

Question 42

Which family of pulse sequences should be chosen to optimize the SNR of MR images?

Answer 42

spin echo

Question 43

A technologist uses a surface coil with a diameter of 5 inches. How deep will adequate signal from the patient’s tissues be generated?

Answer 43

2.5 inches