MEDRADSC 3DE3 Lecture Notes - Lecture 13: Band-Pass Filter, Magnetic Susceptibility, Mononuclear Phagocyte System
20 Aug 2020
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Document Summary
Some may degrade others mask or mimic pathology. Some can be beneficial, demonstrate flow, visualize pathology, characterize lesions. Some irreversible and can only be reduced and not eliminated. Most common image artifact is patient motion. Random movement which produces blurry noise images of periodic motion which creates ghosting. This can occur even outside the anatomical limits. Motion artifact normally in the phase encode direction due to movement of spins between 2 excitations or between phase encoding and signal reading. Signal sampling in the frequency encoding occurs so fast that physiological motion will only produce small amount of spatial blurring in that direction. Periodic: the intensity of ghost images increases with the intensity of the moving structure and with the amplitude of movement. Can show up as increased or decrease of the true image signal. This occurs because of cardiac, breathing etc (occurring in a timely manner) Values relate to the phase sampling interval (tr)
