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147 Cards in this Set
- Front
- Back
increasing the flip angle yields images with |
more t1 info |
|
reducing the flip angle yields images with |
less t1 info |
|
reducing the tr yields images with |
more t1 info |
|
increasing the te yields images with |
more t2 info |
|
increasing the tr yields images with |
less t1 information |
|
reducing the te yields images with |
less t2 info |
|
reducing the te does what to snr |
increases snr |
|
reducing the etl |
increases scan time |
|
increasing the flip angle does what to snr |
increases up to Ernst angle |
|
increasing the matrix does what to snr |
decreases |
|
increasing the slice thickness does what to snr |
increases snr |
|
increasing the nsa does what to scan time |
increases scan time |
|
increasing the slice thickness has what affect on scan time |
doesn't affect scan time |
|
increasing the phase matrix does what to scan time |
increases scan time |
|
increasing the fov does what to scan time |
does not affect scan time |
|
for a given tissue with a given t1 relaxation time and tr, the flip angle,which will result in the max signal for that tissue is |
the Ernst angle |
|
increasing the number of slices in a 2d acquisition does what to scan time |
doesn't affect scan time |
|
increasing the te does what to scan time |
doesn't affect scan time |
|
increasing tr does what to scan time |
increases scan time |
|
when triggering a scan from a pt ecg, the tr of the sequence is determined by the |
patients heart rate |
|
in a fast spin echo sequence the central lines of k space are associated with the |
effective te |
|
the effective te in a fast spin echo pulse sequence determines the |
image contrast |
|
increasing the matrix in the frequency direction from 256 to 512 will |
have no effect on scan time |
|
using a 3d acquisition increasing the number of slices from 64 to 128 does what to scan time |
doubles it |
|
using a 3d acquisition the number of slices allowed when increasing the tr |
is not affected |
|
using a conventional spin echo multi-line sequence, the number of slices allowed when increasing the tr from 20-40ms |
decreases |
|
using a conventional spin echo multislice sequence the number of slices allowed when increasing the te |
increases by a factor of tr/te |
|
to rephase the signal from moving spins, gradient moment nulling techniques use a |
gradient |
|
gradient moment nulling iss most effective when correcting for motion induced signal loss from |
slow constant flow |
|
increasing the number of phase encodings (matrix) from 128 to 256 (by a factor of 2) the SNR |
decreases |
|
a chemical or spectral fat suppression sequence will suppress the signals from fat based on the |
processional frequency of fat |
|
in choosing the direction of phase encoding, the Technologist usually considers the direction in which the |
motion artifacts traverse the least tissue or areas of interest |
|
if a stir sequence using a tr of 3000, a te of 20, and a t1 of 140 produces an image with dark fat and bright water, the contrast in such an image is primarily based on |
t1 |
|
reducing nsa will reduce the scan time and |
decrease the SNR |
|
increasing the number of phase encodings will produce an image with |
decreased vowel volume |
|
doubling the number of signal averaged will |
increase the SNR by the square root of 2 |
|
between slices 2 d acquisitions generally require |
gaps |
|
the SNR will increase in a 3d sequence with an increase in |
fov and number of slices |
|
in a conventional spin echo multislice sequence, it is possible to create multiple images each with different amounts of |
t2 weighting |
|
the time during which the frequency encoding gradient is on |
increases with a reduction in receiver bandwidth |
|
increasing the receiver bandwidth does what to the available etl |
nothing |
|
decreasing the receiver bandwidth does what to number of slices |
decreases |
|
decreasing the receiver bandwidth does what to susceptibility artifact |
increases |
|
decreasing the receiver bandwidth does what to readout time |
increases |
|
decreasing the receiver bandwidth does what to chemical shift |
increases |
|
decreasing the receiver bandwidth does what to snr |
increases |
|
a stir can suppress signal from |
fat and gadolinium enhanced lesions |
|
another name for ti is |
tau |
|
in an inversion recovery pulse sequence, the time between the initializing 180 pulse and the 90 pulse is known as |
ti |
|
in an inversion recovery pulse sequence, image contrast is controlled by |
tr te and ti |
|
2d conventional spin echo multislice pulse sequence scan time equation |
TR * SLICES*NSA* PE |
|
in a gradient echo sequence, reducing the flip angle while holding the TR constant reduces |
saturation |
|
as the te increases |
snr decreases |
|
as the tr increases |
snr increases up to a point |
|
reducing the television does what to contrast based on t2 relaxation times |
reduces |
|
reducing the tr down to or below the t1 relaxation time of the tissue does what to snr and saturation |
decrease snr and increase saturation effects |
|
increasing the te does what to contrast based on t2 relaxation times of tissues |
increases |
|
complete saturation is a condition where |
longitudinal mag is not allowed to recover between excitations |
|
gradient echo sequences use flip angles |
to control saturation effects |
|
the presaturation pulses usually occur |
prior to the excitation pulse |
|
presaturation pulses are often used to |
reduce flow artifacts |
|
in a spin echo sequence the time between the 90 pulse and the 180 pulse is |
.5 TE |
|
the time between excitation pulse is known as |
TR |
|
when using parallel imaging to reduce the acquisition times what happens to snr and spatial resolution |
snr is reduced and spatial resolution isn't affected |
|
in order the reconstruct an image acquired using parallel imaging what may be required |
reference or calibration scan |
|
automated bolus detection,test bolus, and real time Fluoro triggering can all be used for what |
ce mra |
|
the intrinsic contrast mechanism with regard to fmri is |
the bold effect |
|
in 3d tof and using mip technique what appears bright and is the same as flow within a vessel |
tissues or substances with extremely short t1 relaxation times |
|
the basic mri principle with regard to Mr spectroscopy is |
chemical shift |
|
when performing a dynamic perfusion exam of the brain..using gadolinium contrast what is the result of t2 shortening |
reduced Mr signal |
|
changeling the bvakue alters what |
amplitude timing and duration of diffusion gradients |
|
the main purpose of producing/calculating the Adc map is to |
eliminate the t2 shine through |
|
cine studies are often performed on various joints, the main purpose is to |
visualize motion and function |
|
each frame of cardiac cine sequence shows the heart in |
different phases of the cardiac cycle |
|
cardiac cine acquisitions typically utilize what type of pulse sequence |
gradient echo |
|
a major advantage of 2d tof sequence over a 3d tof is the ability to |
image larger areas without saturation of flowing blood |
|
a major advantage of 3d tof techniques over 2d tof is the ability to |
visualize smaller vessels |
|
I'm a phase contrast technique it is possible to use the data to determine the |
direction of blood flow |
|
phase contrast techniques produce images in which the signal intensity withing the vessel is dependent on |
velocity of flowing blood |
|
in a tof sequence flowing blood is hyperintense relative to stationary tissue because of |
flow related enhancement |
|
in a tof sequence the tissue is hyperintense relative to flowing blood because of |
saturation effects |
|
in a spin echo sequence flowing blood is normally seen as a signal void because |
te is too long to image flow and 90/180 pulse are both slice selective |
|
single order gradient moment nulling doesn't compensate for |
accelerated flow or reverse flow |
|
blood flow velocities are greatest |
at the center of a vessel |
|
to minimize the loss of signal due to dephaseling within a voxel what is used |
small vowels and short te |
|
the removal of signal from vessel in an mra sequence is achieved by |
spatial presaturation |
|
the signal intensity on diffusion sequences is related to |
amount of diffusion |
|
the signal intensity on pc mra sequences is related to |
velocity induced Phase shift |
|
the signal intensity of tof mra sequences is related to |
flow related enhancement |
|
the mra sequence that can be made sensitive to any flow velocity is |
3d phase contrast mra |
|
the mra sequence that is sensitive to flow direction is |
3d phase contrast |
|
the mra sequence that is most sensitive to smaller vessels is |
3d tof |
|
the mra sequence that is least sensitive to slow flow is |
3d tof |
|
a major advantage of mra over conventional angiography is that |
multiple views can be produced from a single acquisiton |
|
normal blood flow is known as |
turbulent flow |
|
The swirling blood that occurs just past three area of stenosis is known as |
vortex flow |
|
blood flow at the area of stenosis is known as |
accelerated flow |
|
normal blood flow is known as |
laminar flow |
|
cardiac analysis is performed with a technique using sat bands to assess the wall motion is known as |
myocardial tagging |
|
fourier transformation is performed in the |
array processor |
|
what converts signal data from the fid into the spectrum |
fourier transformation |
|
the technique by which the signal data is modified from the time domain to the frequency domain is known as |
fourier transformation |
|
a 3d dataset that displays what appears to be a 3d image of anatomy is also known as |
volume rendering |
|
to better visualize abdominal organs with and without contrast enhancement what is used |
subtraction |
|
collecting low frequency data points in K space at the start of the scan in spiral fashion is known as |
elliptic centric |
|
collecting low frequency data points in K space at the start of the scan in rectilinear fashion is known as |
centric |
|
in order to produce a high quality reformatted image, the Aquisition voxel should be what |
isotropic |
|
creating images in various planes from a 3d dataset is accomplished by |
multiplanar reformatting |
|
to evaluate the cow 3d tof mra sequences are acquired and background tissue is carved out to provide better visualization..this is called |
segmenting |
|
to evaluate the cow, 3d tof mra sequences are acquired and displayed as an axial view of all the vasculature..this is known as |
collapsed image |
|
the create projection image in mra the technique most commonly employed is |
maximum intensity pixel |
|
acquiring half if the phase views of k space and then interpolation the data for the other half is a technique known as |
half fourier |
|
with conventional spin echo each line of k space is filled in each |
te period |
|
one direction of k space represent phase and the other represents |
frequency |
|
TR*NSA*#PE*#slices is the equation for |
3d volume acquisiton |
|
the slices in 3d acquisiton are produced by |
a phase encoding gradient applied to the slice selection direction |
|
#pe/etl calculates |
number of shotd |
|
in a fse sequence the etl is increased by a factor of 4, what happens to scan time |
increased by factor of 4 |
|
scan time for 2d fse pulse sequence equation |
tr* pe*NSA/etl |
|
tr*#pe*nsa |
equation for 2d ir, 2d gre,2d se |
|
mrv- where should the sat band be placed |
inferior |
|
cow - where should sat band be placed |
superior |
|
carotid arteries, where should say band be placed |
superior |
|
mra of Ivc,where should sat band be placed |
superior |
|
sense, smash, grappa are all what types of imaging |
parallel |
|
in a balanced great acquisition the contrast weighting is |
weighted for the ratio of t2/t1 |
|
what sequence does Ms plaques appear hyperintense relative to csf |
t2 flair |
|
what sequence is used to maximise the bold effect |
gradient echo |
|
an epi sequence is described as |
a train of gradient echos |
|
to null signal from a specific tissue using an inversion recovery sequence, an inversion time that is how much of the t1 relaxation should be used |
69% |
|
a flair sequence suppresses the signal from |
Ms plaques, gadolinium, and fat |
|
gradient echo sequences acquired for the evaluation of hemorrhagic lesions rely on |
susceptibility |
|
gradient echo sequences can yield what two types of characteristics |
t1 or t2* |
|
dynamic enhanced.mra sequences of the renal arteries are performed with the use of |
incoherent gradient echos |
|
gradient echo sequences acquired from fluid are also known as |
coherent, steady state, t2* gradient echos |
|
when a gradient echo sequence is acquired for dynamic contrast enhanced imaging if the liver what is performed |
spoiling |
|
in fse sequence acquired with effective te, scan time can be reduced by the selection of |
longer etl |
|
in fse blurring can be reduced by |
shorter etl |
|
in fse sequence spatial resolution is associated with |
high amplitude phase encoding gradients |
|
in fse sequence the effective te is performed with what type of phase encoding gradients |
low amplitude |
|
the readout gradient is also known as the |
frequency gradient |
|
the gradient that is on during the production of the echo |
frequency |
|
phase encoding is performed when in relation to frequency |
prior |
|
if the tr of a gradient echo pulse sequence is considerably less than the t2 the condition that will exist is |
steady state |
|
the gradient that is on during the production of the echo |
frequency encoding gradient |
|
the 180 pulse corrects for |
Mag field in homogeneity es, chemical shift, mag susceptibility |
|
a typical gradient echo sequence begins with |
alpha pulse that varies with desired image contrast |