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RADT 242: MRI Physics Review Flashcards | StudBud
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RADT 242: MRI Physics Review
RADT 242: MRI Physics Review
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1
Flow artifact can be reduced by:
Gradient moment nulling
all of these
Decreasing TE
Using pre saturation pulses
2
Frequency that exist randomly in space and time is ____?
Phase
Noise
Chemical shift
Signal
3
Which of the following is used to achieve black blood imaging?
douoble IR prep
gradient moment nulling
flow compensation
even echo rephasing
4
In CINE imaging when cardiac gating is used, the number of data points is:
TR x number of slices
effective TR -(trigger delay - trigger window)
effective TR - (trigger window + trigger delay)
R to R interval / effective TR
5
Identify the artifact
Susceptibility
Parallel Imaging
Cross Talk
Zipper
6
The term slew rate refers to the __ of the gradient magnetic field.
strenth and speed of the slope
stength
time to reach the maxium slope
direction
7
Exploits the differences in magnetic suspectibility in oxhemoglobin and deoxyhemoglobin is ___?
Spectroscopy
Perfusion
BOLD
DWI
8
A larger flip angle increases SAR?
False
True
9
Which to the following factors does not affect spatial resolution?
slice thickness
FOV
pixel/voxel size
flip angle
10
Flowing nuclei is out of phase w/ stationary nuclei causing a reduction of signal amplitude within a voxel.
even echo rephasing
intra voxel dephasing
flow phenomena
zipper artefacts
11
Shimming can be accomplished ______.
shielding
passively
actively and passively
actively
12
Phased Array Coils utilize _______ receivers.
zero
soletory
solitary
multiple
13
Spatial resolution can be increased by____?
thick slices
fine matrix
large fov
increase flip angle
14
What is the formula for calculating scan time for a spin echo?
TR x phase encoding steps x NSA / TE
TR x phase encoding steps x NSA
TR x phase encoding steps x NSA / ETL
TR x matrix / fov
15
How much does SNR increase when using Quadrature coils?
25%
50%
10%
40%
16
An increase in FOV or a decrease in matrix by a factor of 2, yields a ____ increase in SNR.
four times
six times
eight times
2 times
17
The body coil located inside the bore is a ___?
Solenoid coil
Gradient coil
Shim coil
RF coil
18
A decrease in voxel volume leads to a decrease in:
chemcial shift
cross talk
aliasing
partial volume averging
19
Fat precesses at a lower frequency than water with a higher field strength magnet can cause:
Truncation
Chemcial shift
Cross talk
Ghosting
20
Increasing phase encoding steps will:
Increases SNR
Increase voxel size
Decreases voxel size
Decrease resolution
21
Interleaving is when alternate slices are excited and divided into two acquisitions to decrease_________________.
chemcial misregistration
zipper
cross excitation
chemcial shift
22
What is it called when a time domain is converted into a frequency domain?
Ohm's Law
Foureir Transform
Faradays Law Domain
Free Induction Decay (FID)
23
The cause of a zipper artefact?
wrap and field inhomgeneity in a gradient echo
Fat and water out of phase
Extraneous RF entering the room
Low field magnetic
24
Which MRA technique uses velocity encoding (VENC) ?
Phase contrast
Time of flight
Contrast enhanced
Digital subtraction
25
The micro-circulation of the delivery of blood to tissue is called:
Effusion
Infusion
Diffusion
Perfusion
26
In slice acquisition in cardiac gating, the available imaging time is:
Effective TR - (trigger window + trigger delay)
Effective TR - (Trigger delay - Trigger window)
TR x number of slices
R to R interval / effective TR
27
Which of the following helps to assist with CNR?
using contrast agents
using chemical pre saturation
all of these
using different weighted images
28
2D TOF is good for imaging slow flow, where as 3D is good for fast flow.
True
False
29
Stationary tissue becomes saturated and flowing nuclei are fresh produce which phenomenon?
Time of Flight
Flow Phenomenon
Intra-voxel dephasing
Entry slice phenomenon
30
Which of the following units is used to measure homogenity?
mT/m
W/kg
ppm
G/cm
31
What is the formula for calculating R-R Interval (Effective TR)?
60,000/BPM
BPM/60, 000
6,000/BPM
1,000/BPM
32
If the ETL in a FSE is 4, how many lines of Kspace is filled with each TR?
1
16
8
4
33
Pulses that nullify signal from flowing nuclei before they enter the FOV?
Even echo rephasing
Compensation
Gradient moment nulling
Spatial Pre-Saturation
34
Which of these will assist with CNR in an image to view pathology?
all of these
SPIR
water saturation
fat saturation
35
Which material has a small magnetic moment?
Paramagnetic
Diamagnetic
Superparamagnetic
Ferromagnetic
36
A 1.5T magnet is equivalent to:
1,500 gauss
150,000 gauss
15,000 gauss
1,500,000 gauss
37
Decreasing receiver bandwidth:
Increases CNR
Increases SNR
Decreases SNR
Decreases CNR
38
Which of the following is a form of Magnetic Resonance Angiography imaging?
time of flight
digital subtraction
All of these
Phase Contrast
39
Susceptibility artifact can be reduced by:
reducing TE
using spin echo
removing metal from patient
all of these
40
In cardiac gating, the TR depends on which of the following?
trigger delay
R to R interval
trigger window
QRS interval
41
What is the difference between pixels and voxels?
Pixel affect contrast in image where voxels do not.
voxels are pixels with a third dimension
Pixels are 3d and voxels are 2d
Pixel offer more SNR than voxels
42
The translation motion of water molecules in any direction on a cellular level is called ___.
osmosis
perfusion
spectroscopy
diffusion
43
An increase in slice thickness will do which of the following?
decrease patrial volume effect
decrease SNR
decrease anatomic coverage
decrease resolution
44
Identify the highlighted area:
TR
TI
ETL
TE
45
What imaging option is used in Bright Blood imaging to enhance signal from blood and CSF?
Double inversion recovery
Double IR prep
Even Echo Rephasing
Gradient moment rephasing
46
The percentage of time that the gradient is permitted to work is defined as:
Gradient strength
Gradient speed
Slew rate
Duty cycle
47
The term rise time refers to the ___ of the gradient magnetic field.
strength
stength and speed of the slope
direction
time to reach the maxium slope
48
For RF coils to work in MR, the B1 fields needs to be _____ to the Bo field.
on top of
in front of
parellel to
perpendicluar or at 90 degrees
49
Which of the following terms refers to signal void artifact caused by fast flowing nuclei in spin echo imaging.
Zipper Artefacts
Intra Voxel Dephasing
Even Echo Rephasing
Flow Phenomena
50
Pre saturation pulses are used to:
increase snr
improve spatial resolution
reduce scan time
reduce flow artifacts
51
Which artifact produces replication of moving anatomy across the image in the phase direction?
Chemical Shift
Ghosting (phase mismapping)
Zipper
Aliasing (phase wrap)
52
The homogeneity of an MR scanner is maximized through a process known as _____.
center frequency
shimming
tuning
fat sat
53
Identify the highlighted area:
ETL
TE
TI
TR
54
Identify the second line of the pulse sequence diagram:
Slice Select
RF
Frequency endoding
Phase encoding
55
Identify the artifact
Chemical Shift
Motion
Susceptibility
Aliasing
56
How to correct for Gibbs artefact?
Decrease number of phase encodings
Increase FOV
Inrease number of phase encodings
Decrease FOV
57
Flowing nuclei in the slice for the excitation may have exited before rephasing. This is called______________.
Even echo rephasing
Intra voxel dephasing
Time of flight phenomenon
Flow phenomena
58
Advantage of increased echo train length is a decrease in scan time, but a disadvantage of:
increased blurring
decreased # of slices
none of these
Increase contrast mix
59
In DWI imaging, ADC maps are used to compensate for which artifact.
Mismapping
Zipper
patrial volue averaging
T2 shine through
60
What determines the number of pixels in the FOV?
voxel
flip agnle
NEX
matrix
61
Signal outside the FOV is mapped inside the fov is called?
ghosting
chemical shift
frequency wrap
phase wrap
62
What is the formula for calculating pixel size?
FOV+Matrix
FOV*Matrix
FOV/Martix
FOV+Phase Matrix+Frequency Matrix
63
Which MRA technique measures transverse magnetization T2 between moving and stationary nuclei?
time of flight
contrast enhancement
phase contrast
digital subtraction
64
Which of the following is not a remedy to reduce phase mismapping?
Swapping phase and frequency
Respiratory Gating or Trigger
Dixon Technique
Pre saturation pulses
65
How to determine pixel size?
TR x phase x nex
Matrix/Fov
FOV/matrix
TR x phase x nex/etl
66
Flow at different velocities that fluctuates randomly is__?
Turbulent flow
Spiral flow
Vortex flow
Laminar flow
67
If the slice thickness is doubled the SNR will________?
Quadruple
Double
Triple
No be affected
68
A decrease in TE does which of the following?
Increases Resolution
Increases SNR
Decreases T1 contrast
Increases T2 contrast
69
Undersampling of data causes a low intensity band though a high intensity area is called?
Cross talk
Magnetic Suspceptibility artefact
Truncation artefact
Zipper artefact
70
Increasing NEX does which of the following?
Decreases scan time
Increase motion artifact
Decreases SNR
Increases SNR
71
What imaging technique is used to compare the chemical composition of normal tissue to abnormal tissue.
Fuctional MRI
Microscopy
BOLD
Spectroscopy
72
What type of flow is in the direction of the slices?
Laminar flow
Co-current flow
Counter-current flow
Turbulent flow
73
Identify the artifact
Cross Talk
Chemical Shift
Aliasing
Motion
