Chapter 3

Question 1

Which gradient is aka the readout gradient?

Answer 1

frequency

Question 2

Match the timing of the slice select, phase encoding and frequency encoding gradients … slice select gradient

Answer 2

During the 90 and 180 in a spin echo, during excitation pulse of a gradient echo.

Question 3

Match the timing of the slice select, phase encoding and frequency encoding gradients … phase encoding gradient

Answer 3

after the excitation pulse.

Question 4

Match the timing of the slice select, phase encoding and frequency encoding gradients … frequency encoding gradient

Answer 4

during collection of the signal.

Question 5

TRUE or FALSE: The top half of data in k-space is identical to the bottom half.

Answer 5

True

Question 6

Match the portion of k-space to its respective amplitude and resolution - central portion

Answer 6

low resolution, high amplitude.

Question 7

Match the portion of k-space to its respective amplitude and resolution - outer portion

Answer 7

high resolution, how aamplitude

Question 8

Match the types of data acquisition … sequential

Answer 8

All the data from slice 1 then all the date from slice 2, etc.

Question 9

Match the types of data acquisition … 2D

Answer 9

1 line of k-space for slice 1 then the same line for slice, 2, etc.

Question 10

Match the types of data acquisition … 3D

Answer 10

Not slices. Acquires an entire volume

Question 11

TRUE or FALSE: K-space is not the image.

Answer 11

True

Question 12

TRUE or FALSE: The scan time is the time to fill k-space.

Answer 12

True

Question 13

Match the polarity of each gradient to the direction traveled through k-space - positive frequence encoding gradient

Answer 13

left to right

Question 14

Match the polarity of each gradient to the direction traveled through k-space - negative frequence encoding gradient

Answer 14

right to left

Question 15

Match the polarity of each gradient to the direction traveled through k-space - positive phase encoding gradient

Answer 15

top half

Question 16

Match the polarity of each gradient to the direction traveled through k-space - negative phase encoding gradient

Answer 16

negative half

Question 17

How fast do we sample frequencies according to the Nyquist theorem?

Answer 17

2x/cycle

Question 18

Match the slice select to their respective transmit bandwidth … thin slices

Answer 18

narrow transmit bandwidth

Question 19

Match the slice select to their respective transmit bandwidth … thick slices

Answer 19

broad transmit bandwidth

Question 20

Match these terms from Chapter 3 … FOV

Answer 20

Steepness of the slope of the frequence encoding gradient determines the size of the anatomy

Question 21

Match these terms from Chapter 3 … sampling time

Answer 21

Duration of the readout gradient. Aka: acquisition window

Question 22

Match these terms from Chapter 3 … FFT

Answer 22

mathmatical process that converts time into a frequency domain

Question 23

Match these terms from Chapter 3 … aliasing

Answer 23

artefact caused by sampling too infrequently

Question 24

Match these terms from Chapter 3 … range of frequencies we wish to sample during the readout

Answer 24

receive bandwidth

Question 25

What is the mathematical process that converts time into a frequency domain?

Answer 25

Fast Fourier Transform

Question 26

Match the gradients to their slice selection ... X

Answer 26

sagittal

Question 27

Match the gradients to their slice selection ... Z

Answer 27

axial

Question 28

Match the gradients to their slice selection ... Y

Answer 28

coronal

Question 29

Match the gradients to their slice selection ... combo

Answer 29

oblique

Question 30

what does the phase gradient do

Answer 30

encodes along the short axis of anatomy

Question 31

what does the frequency gradient do

Answer 31

encodes along the long axis of anatomy

Question 32

Which gradient determines the FOV?

Answer 32

frequence

Question 33

How often must we sample frequencies, according to the Nyquist Theorem?

Answer 33

Twice per cycle

Question 34

What is another term for the duration of the readout gradient?

Answer 34

Sampling time

Question 35

Which gradient performs slice selection for coronal slices?

Answer 35

Y gradient

Question 36

When is the slice select gradient switched on during a spin echo pulse sequence?

Answer 36

During the 90 and 180 degree pulses

Question 37

Which gradient locates signal along the LONG axis of the anatomy?

Answer 37

Frequency encoding gradient

Question 38

A data point contains both phase and frequency information

Answer 38

true

Question 39

During a typical spin echo sequence, there are three gradient applications. In chronological order they are:

Answer 39

Slice select, Phase encoding, Frequency encoding

Question 40

To achieve THIN slices would we use a narrow or broad transmit bandwidth?

Answer 40

Narrow

Question 41

To achieve thin slices, do we need a STEEP or SHALLOW slice select slope?

Answer 41

STEEP

Question 42

Which part of K space do shallow phase gradients fill?

Answer 42

Central lines of K space, both positive and negative

Question 43

K space is not the image.

Answer 43

True

Question 44

What is the unit of K space?

Answer 44

Radians per centimeter

Question 45

Which part of K space do steep phase gradients fill?

Answer 45

Outer lines of K space, both positive and negative

Question 46

What is another name for the frequency encoding gradient?

Answer 46

Readout gradient

Question 47

What kind of information is contributed by data collected in the central lines of K space? (Select all that apply)

Answer 47

* Signal | * Contrast

Question 48

What artifact occurs if we sample frequencies less than once per cycle?

Answer 48

Aliasing

Question 49

Data in K space are symmetrical.

Answer 49

True

Question 50

The scan time is the time to fill K space.

Answer 50

True

Question 51

What controls the polarity of a gradient?

Answer 51

The direction of the current through the gradient coil

Question 52

What does the slope of the frequency encoding gradient determine? (Select all that apply)

Answer 52

* The size of the anatomy covered along the frequency encoding axis * The FOV

Question 53

What does the phase encoding gradient do?

Answer 53

Encode data along the SHORT axis of the anatomy

Question 54

Which gradient performs slice selection for sagital slices?

Answer 54

X gradient

Question 55

When is the phase encoding gradient switched on in a pulse sequence?

Answer 55

Usually just before the application of the 180 degree rephasing pulse

Question 56

Where are the data points collected by the system stored?

Answer 56

K space

Question 57

The phase axis of K space is vertical and is centered in the middle of K space perpendicular to the frequency axis.

Answer 57

True

Question 58

What kind of information is contributed by data collected in the outer lines of K space? (Select all that apply)

Answer 58

Resolution

Question 59

Phase encoding gradient positive fills the bottom half of K space.

Answer 59

False | Phase encoding gradient positive fills the top half of K space - see page 96 in the text

Question 60

Which gradient performs phase encoding for coronal slices?

Answer 60

Y gradient

Question 61

If a 512 phase matrix is selected, which k-space lines are likely to be filled in a normal acquisition?

Answer 61

256, 0 to -255

Question 62

Which gradient lies along the horizontal axis of a typical superconducting MRI system?

Answer 62

The X gradient | See page 61 in the text.

Question 63

what is the unit of K space

Answer 63

radians/centimenter

Question 64

what do data in central lines contribute to

Answer 64

signal and contrast

Question 65

what do data in outer lines contribute to

Answer 65

resolution