Unit 7 Quiz Flashcards
What is the primary goal of protocol optimization in MRI?
Enhancing image quality
Spin echo pulse sequences generally have _____ that gradient echo sequences, as all the longitudinal magnetization is converted into transverse magnetization by the flip angle.
More signal
The _________ controls the amount of transverse magnetization that is allowed to decay before an echo is collected.
TE
This is the number of times data are collected with the same amplitude of phase encoding slope.
NEX/NSA
The __________ is the ratio of amplitude of the signal received to the average amplitude of the noise.
SNR
The _____________ controls the amount of transverse magnetization that is created which induces a signal in the coil.
Flip angle
___________ is random as it is in a different position each time data are stored.
Noise
In large voxels, individual signal intensities are averaged together & are not represented as distinct within the voxel. This results in _______________________
Partial voluming
______ always provide better spatial resolution than _____ as the image is equally resolved along both the frequency & phase axis.
Square pixels / rectangular pixels
The dimensions of the FOV in the phase direction is reduced compared to that in the frequency direction & so should be used when ___________________
Imaging anatomy that fits into a rectangle
Large voxels result in __________________, as small structures are not resolved so well
Low spatial resolution
Of the three main factors that affect scan time which one does not fit?
TE
With respect to voxel size it is directly affected by all but one, which?
Flip angle
