PHASE AND FREQUENCY & FAST IMAGINING TECHNIQUES

Question 1

The main function of Fourier transform in MR image reconstruction is to:

Answer 1

Convert time domain to frequency domain

Question 2

Frequency can be defined as:

Answer 2

The rate of phase change

Question 3

A magnetic field that varies over distance is known as:

Answer 3

A gradient magnetic field

Question 4

The steepness or amount of slope of a gradient magnetic field is the

Answer 4

Amplitude

Question 5

The physical gradient that varies the magnetic field in the head to foot direction is the:

Answer 5

Z-gradient

Question 6

The physical gradient that varies the magnetic field in the right to left direction is:

Answer 6

X-gradient

Question 7

The physical gradient that varies the magnetic field in the anterior to posterior direction is the:

Answer 7

Y-gradient

Question 8

Along a gradient magnetic field, the highest frequencies would:

Answer 8

At the ends

Question 9

Using the logical notation, the gradient performing phase encoding would be annotated with the letter

Answer 9

Y

Question 10

Using the logical notation, what is the order in which the gradients are applied in a standard acquisition?

Answer 10

Z,Y,X

Question 11

Slice thickness is affected by the _______ of the slice selecting gradient:

Answer 11

Amplitude

Question 12

What affects slice thickness?

Answer 12

Transmit bandwidth

Question 13

What will result in a thinner slice?

Answer 13

Higher amplitude of the slice selecting gradient

Question 14

What physical gradient would be utilized to selectively excite a sagittal slice?

Answer 14

X

Question 15

To produce a single axis oblique:

Answer 15

Two gradients would be used in combination

Question 16

The readout gradient is also known as the what gradient?

Answer 16

Frequency encoding

Question 17

Selecting a 256 frequency matrix would result in how many data points being collected or sampled during the formation of the echo?

Answer 17

256

Question 18

The gradient which steps through different amplitudes during the scan is the:

Answer 18

Phase encoding

Question 19

Increasing what will result in a direct decrease in scan time?

Answer 19

Phase matrix

Question 20

The number of times each phase line of K-space is samples is:

Answer 20

NSA

Question 21

Increasing the NSA will result in:

Answer 21

Reduction in noise

Question 22

The method of filling K-space which begins with the maximum negative phase steps through zero then through positive steps is known as:

Answer 22

Linear

Question 23

Which of the following K-space filling methods would likely preferred when performing a contrast enhance MRA:

Answer 23

Centric

Question 24

With regard to MR raw data, the data points which provide the greatest signal contribution are:

Answer 24

Low frequencies

Question 25

Where in K-space is high frequency date:

Answer 25

Outer

Question 26

With regard to MR raw date, edge detail is provided by:

Answer 26

High frequencies

Question 27

Using a conventional spin echo sequence, increasing the TE from 20msec to 80 msec will have what effect on the number of slices allowed?

Answer 27

Decrease

Question 28

Using a conventional 2DFFT acquisition, what would result in the least amount of cross-talk?

Answer 28

Bigger slice gap

Question 29

For a typical 2DFFT acquisition of 6 slices, the order in which the slices will be excited are:

Answer 29

1,3,5,2,4,6

Question 30

In a 3DFFT acquisition, the slices are:

Answer 30

Reconstructed

Question 31

In a 3DFFT acquisition, SNR is proportional to the:

Answer 31

The square root of the number of slices

Question 32

Acquired voxels which are equal in all three dimensions are referred to as:

Answer 32

Isotropic

Question 33

Reformatting image date into another plane is done through a process known as:

Answer 33

MPR

Question 34

A technique used to reduce scan time which does not fully sample high frequency data but rather replaces it with zeros is known as:

Answer 34

Zero-fill

Question 35

A scan time reduction technique which reduces the phase matrix and phase FOV by the amount is referred to as:

Answer 35

Rectangular FOV

Question 36

Which scan time reduction technique may require a reference or calibration scan prior to the actual acquisition?

Answer 36

Parallel imaging

Question 37

In a FSE sequence what parameter determines how many lines of K-space data will be acquired in a single TR period?

Answer 37

ETL

Question 38

In FSE the effective TE is associated with:

Answer 38

Low frequency data

Question 39

Spin echo EPI is most often used to acquire what type of MRI studies?

Answer 39

Diffusion weighted images

Question 40

When acquiring a single shot EPI what matrix selection will have least distortion artifacts?

Answer 40

128 X 128