Experiments for two MR imaging theories of motion phase sensitivity.
Two theories of motion-sensitive phase shifts in magnetic resonance (MR) imaging result in different mathematical predictions of the observed effects of gradient modulation-induced motion artifacts. The consequences are critical for gradient waveform designed to minimize motion artifact contaminations from time-dependent motion sensitivity. To resolve this discrepancy with a test case (the monopolar waveform of a commonly used, discretely pulsed encoding phase gradient), computer integration of the fundamental Bloch equations for MR imaging with motion was performed. Simulation images for constant and erratic motion showed almost complete agreement with the predictions of the transport integral solutions for motion phase sensitivity; the artifact was solely time-of-flight oblique flow misregistration. Conventional method-of-moments gradient moment nulling compensations produced greater motion artifacts in experiments than did use of no waveform compensation at all. Transport equation solutions implied second-integral zeroing instead; these modifications eliminated the artifacts.
Moran
P R
PR
Bowman Gray School of Medicine, Wake Forest University, Winston-Salem, NC 27103.
D008279:Magnetic Resonance Imaging; D009038:Motion; D055585:Physical Phenomena; D010825:Physics