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