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HSC3007 MRI > MRI in Practice Notes > Flashcards

MRI in Practice Notes Flashcards

1
Q

MR active nuclei are __

A

nuclei with odd number / atomic weight

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2
Q

Protons consists of __ quarks - __ spin up & __ spin down

A

3; 2; 1

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3
Q

protium

A

hydrogen isotope

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4
Q

k-space

A

array of numbers representing spatial frequency in x & y axis of MR image; fourier transform of MR image

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5
Q

The individual points (kx,ky) in k-space __ one-to-one with individual pixels (x,y) in the image

A

do not correspond

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6
Q

each k-space contains ___ about every pixel in final image

A

spatial frequency & phase information

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7
Q

Time of Echo

A

time between middle of 1st RF to peak of spin echo

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8
Q

what is the purpose of the 180 degree pulse in spin echo

A

refocuses non-moving spins whose phases have been scattered by constant field distortions & inhomogeneities

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9
Q

what does the 180 degree pulse not correct for

A

T1 or true T2 effects due to random processes at atomic/molecular level

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10
Q

the amplitude of each echo in multi-echo spin echo progressively decreases due to __

A

T2 decay

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11
Q

fast spin echo

A

multiple 180 degree pulses & echoes follow each 90 degree pulse

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12
Q

fast spin echo utilizes __

A

different phase encoding gradients with each 180 degree pulse

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13
Q

The liquid helium used to cool the magnetics’ coil has a temperature of __

A

-452 degrees fahrenheit

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14
Q

Maximum SNR is achieved when the NMV is at _______ to a receiver coil.

A

90 degrees

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15
Q

How many 90 RF pulses are used in 1 TR of a Fast Spin Echo sequence?

A

1

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16
Q

How many pairs of gradients are there?

A

3

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17
Q

The flip angle that produces a spin‐echo is _______.

A

180 degrees

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18
Q

The difference in signal intensity between tissues is called _______.

A

contrast

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19
Q

T1 is the time taken for the transverse NMV to return to equilibrium at B0.

True or False

A

False

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20
Q

T2 is the time for the transverse NMV to decay to its original value.

True or False

A

False

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21
Q

How many RF pulses are needed to produce a single spin echo?

A

2

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22
Q

Coils are orientated at what angle to the NMV?

A

parallel / orthogonal / perpendicular

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23
Q

Patients are at risk of cardiac stimulations during MRI.

True or False

A

False

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24
Q

For a Time of Flight MRA of the carotids ARTERIES, the saturation pulse is placed _______ to the slices/slab

A

superior

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25
Q

When in the equilibrium state, protons precess _______.

A

at larmor frequency

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26
Q

Components of the Larmor equations are: Precessional frequency, Gyromagnetic ratio, and _______.

A

field strength

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27
Q

Why does air not give signal on MR images?

A

lack of H+

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28
Q

Slice thickness is determined by the _______?

A

Bandwidth of the Excitation pulse

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29
Q

At equilibrium, the spins are precessing in phase, about the main magnetic field B0.

True or False

A

False

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30
Q

The process of tissues giving off energy to the _______ is called _______?

A

lattice;T1

31
Q

Another name for proton density is _______?

A

hydrogen & spin density

32
Q

Another name for T1 relaxation is _______?

A

Longitudinal Relaxation

33
Q

The RF pulses used in MR imaging are considered to be

A

Non‐ionizing and low energy

34
Q

The gyromagnetic ratio of hydrogen is measured in _______?

A

MHz

35
Q

In a Spin Echo sequence, to get a T1w image, the TE is ___

A

twice the time between 90 and 180 pulse

36
Q

An Inversion Recovery sequence (eg STIR or FLAIR) sequence starts off with a _______pulse .

A

180 degrees

37
Q

A spin-echo sequence …

A

May not produce T2* weighted images

38
Q

An excitation pulse will flip the longitudinal NMV into the _______ if the RF pulse has the same _______ as the slice.

A

x/y; precessional frequency

39
Q

What tissue has a Long T1 and Long T2?

A

CSF / water

40
Q

Another name for T2 relaxation is _______?

A

transverse relaxation

41
Q

To produce a gradient echo, the sequence lacks a _______.

A

180 degrees refocusing pulse

42
Q

Which one of the following will Fourier transform be applied to?

A

K-space

43
Q

Turning on the frequency encode gradients, will change __

A

both the frequency and phase of the spins

44
Q

In a T1 weighted image, which choice is correct for brightest to darkest tissue

A

Fat, muscle, water

45
Q

The magnetic moment possessed by a hydrogen proton comes from the proton having _______.

A

spins

46
Q

When a conductor loses electrical resistance at low temperatures, it means it is a _______?

A

superconductor

47
Q

Noise is present in all electronic equipment.

True or False

A

True

48
Q

Which best describes a surface coil?

A

Used to selectively increase signal from a region

49
Q

Fat Saturation may be achieved by utilising the fact that fat and water

A

have different precessional frequencies & T1 timings

50
Q

How many RF pulses are needed to produce an FID echo?

A

1

51
Q

Hydrogen density is determined by _______.

A

Number of protons in a tissue

52
Q

The result of the excitation pulse is _______.

A

Protons precess in phase

53
Q

Magnetic susceptibility is what?

A

A tissue’s ability to be magnetized

54
Q

Signal in a coil is _______ through _______.

A

generated, induction

55
Q

The inherent body coil is a _______ coil.

A

Transmit/Receive

56
Q

Flip Angle is determined by :

A

How long the B1 field is applied

57
Q

A vector has what two properties?

A

Amplitude / Magnitude and Direction

58
Q

In a T2 weighted image, which choice is correct for darkest to brightest tissue

A

Muscle, fat, water

59
Q

A gradient echo can be PD, T1 or T2* weighted depending on the

A

TR, TE and Flip Angle

60
Q

Fat Saturation is typically applied

A

Before excitation

61
Q

In Diffusion weighted imaging (DWI), the desired contrast depends on

A

water movement between the cells

62
Q

The B₁ Field is produced by the _______.

A

RF Transmission Coil

63
Q

The distribution or concentration of hydrogen spins describes what?

A

PD

64
Q

In a hydrogen density weighted image, the short TE will decrease the _______ and a long TR will decrease the _______.

A

T2, T1

65
Q

As the TE is increased, what can be said about the image contrast?

A

more T2 weighted

66
Q

There are three magnetic states of material. Ferrous, Diamagnetic, and _______

A

Paramagnetic

67
Q

Which RF pulse imparts the largest amount of transverse net magnetization?
60, 80, 180, 45

A

80 degrees

68
Q

A gradient echo sequence is affected by __

A

spin-spin, susceptibility, inhomogeneity

69
Q

Which RF pulse imparts the largest amount of energy into a tissue?

A

180°

70
Q

in acute haemorrhage (1-2 days), blood appears

A

Dark on T2*

71
Q

what factors decrease such that spatial resolution increases

A

FOV / Matrix / Voxel Size
thinner slices

72
Q

when phase encoding steps __, spatial resolution increases

A

increases

73
Q

when receiver bandwidth __, SNR increases

A

decreases

74
Q
A

HSC3007 MRI (10 decks)

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