Special procedures Flashcards
normal blood flow (demonstarted by a parabolic blood flow profile) is known as
laminar flow
blood flow at the area of a stenosis is known as
accelerated flow
swirling blood flow that occurs just past the area of stenosis is known as
vortex flow
normal blood flow is known as
laminar
a major advantage of MRA over conventional angiography is taht
multiple views can be produced from a single acquisition
the MRA sequence that is least sensitive to slow flow is
3D TOF
the MRA sequence that is most sensitive to smaller vessels is
3D TOF
the MRA sequence that is sensitive to flow direction is
3D phase contrast MCA (PC MRA)
the MRA sequence that can be made sensitive to any flow velocity is
3D PC MRA
the signaly intensity of TOF MRA sequences is related to
flow related enhancement
the signal intensity of PC MRA sequences is related to
velocity induced phase shift
the signal intensity on diffusion sequences is related to
amount of diffusion
the followoing are important in MRA sequences to minimize the loss of signal due to dephasing within a voxel
small voxels
short TE
blood flow velocities are greatest
at the center of a vessel
single order gradient moment nulling does not compensate for
accelerated flow
reverse flow
in a spin echo sequence flowoing blood is noirmally seen as a signal void because the
TE is too long to image flow
90 pulse and 180 pulse are both slice selective
in a vessel with a plaque producing a high degree of stenosis the velocity of the blood flow in the center point of stenosis is
increased
in TOF sequences the tissue is HYPOintense relative to flowoing blood because of the
saturatoin effects
in TOF sequence, flowoing blood is HYPERintense relative to stationary tissue because of the
flow related enhancement
phase contrast technioques produce images in which the signal intensity within the vessel is dependent on the
velocity of flowoing blood
in a phase contrast technique it is possible to use the data to determine the
directoin of blood flow
a major advantage of 3D TOF techniques over 2D TOF is the ability to
visualize smaller vessels
a major advantage of 2D TOF over 3D TOF is the ability to
image a larger area without saturation of the flowoing blood
cardiac cine acquisitions typically utilize
a gradient echo pulse sequence
each from of cardiac cine sequence displays the heart
in different phases of the cardiac cycle
cine studies are often performed on various joints. the main purpose of such a study is to
visualize motion and function
which of the following would result in an image with the treatest amount of diffusion weighting
b-value 1100
the main purpose of producing/calculating an ADC map is to
eliminate the T2 shine through
changing the b value alters the
amplitude, timing, and or duration of the diffusion gradients
when performing a dynamic perfusion exam of the brain utilizing a gadolinium base MR contrast agent, the result of the T2* shortening is
reduced MR signal
the basic MR principle with regard to MR spectroscopy is
chemical shift
have acquired a 3D TOF when producing an MRA projection image set upsing MIP technique, which of the following can appear bright and therefore the same as flow within a vessel
tissues or substances with extremely short T1 relaxatoin time
the intrinsic contrast mechanism with regard to fMRI is
the BOLD effect
all of the techniques can be utilized to optimally time the start of a contrast enhanced MRA
automated bolus detectoin
test bolus
real time.flouro triggering
in order to reconstruct an image acquired using parallel imaging which of the folloiwng may be required
reference or calibration scan
when using parallel imagin to reduce acqwuisition times, which of the followoing is always true
SNR is not affected unless the accelertion factor is greater than 2
