Brainscape's Knowledge GenomeTM

Browse over 1 million classes created by top students, professors, publishers, and experts.


See full index

Physics > Chapter 3 > Flashcards

Chapter 3 Flashcards

You may prefer our related Brainscape-certified flashcards:
Physics 101 flashcards AP® Physics flashcards
1
Q

Which gradient is aka the readout gradient?

A

frequency

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

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

A

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

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

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

A

after the excitation pulse.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

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

A

during collection of the signal.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

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

A

True

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

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

A

low resolution, high amplitude.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

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

A

high resolution, how aamplitude

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

Match the types of data acquisition … sequential

A

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

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

Match the types of data acquisition … 2D

A

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

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

Match the types of data acquisition … 3D

A

Not slices. Acquires an entire volume

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

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

A

True

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

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

A

True

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

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

A

left to right

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

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

A

right to left

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

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

A

top half

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

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

A

negative half

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

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

A

2x/cycle

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
18
Q

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

A

narrow transmit bandwidth

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
19
Q

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

A

broad transmit bandwidth

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
20
Q

Match these terms from Chapter 3 … FOV

A

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

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
21
Q

Match these terms from Chapter 3 … sampling time

A

Duration of the readout gradient. Aka: acquisition window

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
22
Q

Match these terms from Chapter 3 … FFT

A

mathmatical process that converts time into a frequency domain

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
23
Q

Match these terms from Chapter 3 … aliasing

A

artefact caused by sampling too infrequently

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
24
Q

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

A

receive bandwidth

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
25
Q

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

A

Fast Fourier Transform

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
26
Q

Match the gradients to their slice selection … X

A

sagittal

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
27
Q

Match the gradients to their slice selection … Z

A

axial

28
Q

Match the gradients to their slice selection … Y

A

coronal

29
Q

Match the gradients to their slice selection … combo

A

oblique

30
Q

what does the phase gradient do

A

encodes along the short axis of anatomy

31
Q

what does the frequency gradient do

A

encodes along the long axis of anatomy

32
Q

Which gradient determines the FOV?

A

frequence

33
Q

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

A

Twice per cycle

34
Q

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

A

Sampling time

35
Q

Which gradient performs slice selection for coronal slices?

A

Y gradient

36
Q

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

A

During the 90 and 180 degree pulses

37
Q

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

A

Frequency encoding gradient

38
Q

A data point contains both phase and frequency information

A

true

39
Q

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

A

Slice select, Phase encoding, Frequency encoding

40
Q

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

A

Narrow

41
Q

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

A

STEEP

42
Q

Which part of K space do shallow phase gradients fill?

A

Central lines of K space, both positive and negative

43
Q

K space is not the image.

A

True

44
Q

What is the unit of K space?

A

Radians per centimeter

45
Q

Which part of K space do steep phase gradients fill?

A

Outer lines of K space, both positive and negative

46
Q

What is another name for the frequency encoding gradient?

A

Readout gradient

47
Q

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

A
  • Signal

* Contrast

48
Q

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

A

Aliasing

49
Q

Data in K space are symmetrical.

A

True

50
Q

The scan time is the time to fill K space.

A

True

51
Q

What controls the polarity of a gradient?

A

The direction of the current through the gradient coil

52
Q

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

A
  • The size of the anatomy covered along the frequency encoding axis
  • The FOV
53
Q

What does the phase encoding gradient do?

A

Encode data along the SHORT axis of the anatomy

54
Q

Which gradient performs slice selection for sagital slices?

A

X gradient

55
Q

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

A

Usually just before the application of the 180 degree rephasing pulse

56
Q

Where are the data points collected by the system stored?

A

K space

57
Q

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

A

True

58
Q

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

A

Resolution

59
Q

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

A

False

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

60
Q

Which gradient performs phase encoding for coronal slices?

A

Y gradient

61
Q

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

A

256, 0 to -255

62
Q

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

A

The X gradient

See page 61 in the text.

63
Q

what is the unit of K space

A

radians/centimenter

64
Q

what do data in central lines contribute to

A

signal and contrast

65
Q

what do data in outer lines contribute to

A

resolution

Physics (15 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2024 Bold Learning Solutions. Terms and Conditions