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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
When in the equilibrium state, protons precess _______.
at larmor frequency
26
Components of the Larmor equations are: Precessional frequency, Gyromagnetic ratio, and _______.
field strength
27
Why does air not give signal on MR images?
lack of H+
28
Slice thickness is determined by the _______?
Bandwidth of the Excitation pulse
29
At equilibrium, the spins are precessing in phase, about the main magnetic field B0. True or False
False
30
The process of tissues giving off energy to the _______ is called _______?
lattice;T1
31
Another name for proton density is _______?
hydrogen & spin density
32
Another name for T1 relaxation is _______?
Longitudinal Relaxation
33
The RF pulses used in MR imaging are considered to be
Non‐ionizing and low energy
34
The gyromagnetic ratio of hydrogen is measured in _______?
MHz
35
In a Spin Echo sequence, to get a T1w image, the TE is ___
twice the time between 90 and 180 pulse
36
An Inversion Recovery sequence (eg STIR or FLAIR) sequence starts off with a _______pulse .
180 degrees
37
A spin-echo sequence ...
May not produce T2* weighted images
38
An excitation pulse will flip the longitudinal NMV into the _______ if the RF pulse has the same _______ as the slice.
x/y; precessional frequency
39
What tissue has a Long T1 and Long T2?
CSF / water
40
Another name for T2 relaxation is _______?
transverse relaxation
41
To produce a gradient echo, the sequence lacks a _______.
180 degrees refocusing pulse
42
Which one of the following will Fourier transform be applied to?
K-space
43
Turning on the frequency encode gradients, will change __
both the frequency and phase of the spins
44
In a T1 weighted image, which choice is correct for brightest to darkest tissue
Fat, muscle, water
45
The magnetic moment possessed by a hydrogen proton comes from the proton having _______.
spins
46
When a conductor loses electrical resistance at low temperatures, it means it is a _______?
superconductor
47
Noise is present in all electronic equipment. True or False
True
48
Which best describes a surface coil?
Used to selectively increase signal from a region
49
Fat Saturation may be achieved by utilising the fact that fat and water
have different precessional frequencies & T1 timings
50
How many RF pulses are needed to produce an FID echo?
1
51
Hydrogen density is determined by _______.
Number of protons in a tissue
52
The result of the excitation pulse is _______.
Protons precess in phase
53
Magnetic susceptibility is what?
A tissue's ability to be magnetized
54
Signal in a coil is _______ through _______.
generated, induction
55
The inherent body coil is a _______ coil.
Transmit/Receive
56
Flip Angle is determined by :
How long the B1 field is applied
57
A vector has what two properties?
Amplitude / Magnitude and Direction
58
In a T2 weighted image, which choice is correct for darkest to brightest tissue
Muscle, fat, water
59
A gradient echo can be PD, T1 or T2* weighted depending on the
TR, TE and Flip Angle
60
Fat Saturation is typically applied
Before excitation
61
In Diffusion weighted imaging (DWI), the desired contrast depends on
water movement between the cells
62
The B₁ Field is produced by the _______.
RF Transmission Coil
63
The distribution or concentration of hydrogen spins describes what?
PD
64
In a hydrogen density weighted image, the short TE will decrease the _______ and a long TR will decrease the _______.
T2, T1
65
As the TE is increased, what can be said about the image contrast?
more T2 weighted
66
There are three magnetic states of material. Ferrous, Diamagnetic, and _______
Paramagnetic
67
Which RF pulse imparts the largest amount of transverse net magnetization? 60, 80, 180, 45
80 degrees
68
A gradient echo sequence is affected by __
spin-spin, susceptibility, inhomogeneity
69
Which RF pulse imparts the largest amount of energy into a tissue?
180°
70
in acute haemorrhage (1-2 days), blood appears
Dark on T2*
71
what factors decrease such that spatial resolution increases
FOV / Matrix / Voxel Size thinner slices
72
when phase encoding steps __, spatial resolution increases
increases
73
when receiver bandwidth __, SNR increases
decreases
74

HSC3007 MRI (10 decks)

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