what are additional RF pulse called that is used to nullify signal from flowing nuclei
prior to excitation?
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pre-saturation
-acquire sound echoes at a multiple of the first TE
-nuclei have to be given the same amount of time to rephrase as they were given to
dephase
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Even-echo raphasing
,spatial pre-saturation pulses can be used to
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1. nullify specific tissue signals
2. reduce flow artifacts
3. reduce aliasing
wrap around
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aliasing
What is the unit of measurement for velocity encoding (VENC)?
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cm/sec
Changing the number of phase encoding steps will directly affect which of the
following?
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, scan time
The scan time can be determined by
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1. NEX
2. Number of phase encoding
gradient moment nulling is used primarily for what type of contrast weighting?
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2. T2
3. T2*
o Not suitable for slow flow
o Limited anatomical coverage
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disadvantages of 3D-TOF MRA
Which of the following will improve signal in entry slice phenomenon?
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, Long TR
loss of transverse magnetization
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T2 relaxation
Partial volume averaging exists when
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many tissues are averaged into one voxel
-parabolic flow, flow at different but consistent velocities
-flow at center is faster than flow near walls
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Laminar Flow
blood oxygen level dependent
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prior to excitation?
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pre-saturation
-acquire sound echoes at a multiple of the first TE
-nuclei have to be given the same amount of time to rephrase as they were given to
dephase
Give this one a try later!
Even-echo raphasing
,spatial pre-saturation pulses can be used to
Give this one a try later!
1. nullify specific tissue signals
2. reduce flow artifacts
3. reduce aliasing
wrap around
Give this one a try later!
aliasing
What is the unit of measurement for velocity encoding (VENC)?
Give this one a try later!
cm/sec
Changing the number of phase encoding steps will directly affect which of the
following?
Give this one a try later!
, scan time
The scan time can be determined by
Give this one a try later!
1. NEX
2. Number of phase encoding
gradient moment nulling is used primarily for what type of contrast weighting?
Give this one a try later!
2. T2
3. T2*
o Not suitable for slow flow
o Limited anatomical coverage
Give this one a try later!
disadvantages of 3D-TOF MRA
Which of the following will improve signal in entry slice phenomenon?
Give this one a try later!
, Long TR
loss of transverse magnetization
Give this one a try later!
T2 relaxation
Partial volume averaging exists when
Give this one a try later!
many tissues are averaged into one voxel
-parabolic flow, flow at different but consistent velocities
-flow at center is faster than flow near walls
Give this one a try later!
Laminar Flow
blood oxygen level dependent
Give this one a try later!
