Data Acq Flashcards
in a vessel with a plaque producing a high degree of stenosis, the velocity of the blood flow in the center point of the stenosis:
A - increased
B - decreased
C - reverse
D - unaffected
increased
Phase contrast techniques produce images in which the signal intensity within the vessel is dependent on (among other parameters) the:
A - velocity of flowing blood
B - T1 of tissue
C - FOV selected
D - number of phase encoding views
A - velocity of flowing blood
In a phase contrast technique, it is possible to use the data to determine the:
A - exact size of vessel lumen
B - direction of blood flow
C - temporal displacement of vessel
D - percentage stenosis of a lesion
direction of blood flow
having acquired a 3D TOF, when producing an MRA projection image set using the MIP technique, which can appear bright and therefore the same as flow within a vessel?
A - tissues with long T2 relaxation times
B - tissues or substances with extremely short T1 relaxation times
C - polycystic astrocytoma
D - any substance with an extremely short T2 relaxation time
tissues or substances with extremely short T1 relaxation times
In order to reconstruct an image acquired using parallel imaging, which may be required?
a- test bolus
b - reference or calibration scan
c - back projection
d - half fourier acquisiton
b - calibration scan
when using parallel imaging to reduce acquisition times, what is always true
a - scan time is reduced and spatial resolution is increased
b - spatial resolution is reduced the greater the acceleration factor selected
c - snr is not affected unless acceleration factor is greater than 2
d - snr is reduced and spatial resolution is unaffected
d - snr is reduced and spatial resolution is unaffected
gradient echo sequences use flip angles:
a - less than 90
b - that vary between pulse repetitions
c - to control saturation effects
d - to reduce SAR for larger patients
to control saturation effects
reducing the TR down to or below the T1 relaxation time of the tissue:
a - decreases the signal to noise ratio of the image
b - reduces the contrast based on T2 relaxation times of the tissues
c - increases saturation effects
d - a and c
d
in gradient echo sequence, reducing flip angle while holding the TR constant reduces:
a - T2* contrast weighting
b - spin density contrast weighting
c - saturation
d - scan time
saturation
in an inversion recovery pulse sequence, image contrast is controlled by
a - TR and TE only
b - TI only
c - TI and TE only
d - TR, TE, and TI
d - TR, TE and TI
the number of shots is calculated by:
PEs/ETL
to keep scan time at a minimum, how is diffusion imaging typically performed
single shot EPI acquisition
the technique whereby a portion of the lines of k space are ‘sampled’ and ‘filled’ and the remaining lines are interpolated is known as all of the following except:
a- half fourier
b - partial fourier
c- fractional fourier
d - interleaved acquisition
d
in a 3D acquisition, the slices are produced by:
a - a phase encoding gradient applied in the slice selection direction
b- multiple 180 pulses along the slice selection direction
c - sampling multiple lines of K space per pulse sequence repetition
d - vary accurate RF pulses
a
to evaluate the circle of Willis, 3D TOF MRA sequences are acquired and displayed as an axial view of all of the vasculature. This is known as:
a - multiplaner reconstruction
b - segmented image
c - minimum intensity pixel
d - collapsed image
d - collapsed image
