PULSATILE FLOW ARTIFACTS IN 3D MAGNETIC-RESONANCE-IMAGING

Some of the important features of how pulsatile flow generates artifac ts in three-dimensional magnetic resonance imaging are analyzed and de monstrated. Time variations in the magnetic resonance signal during th e heart cycle lead to more complex patterns of artifacts in 3D imaging than in 2D imaging. The appearance and location of these artifacts wi thin the image volume are shown to be describable as displacements alo ng a line in a plane parallel to that defined by the phase and volume encode directions. The angle of the line in the plane depends solely u pon the imaging parameters while the ghost displacement along the line is proportional to the signal modulation frequency. Aliasing of these ghosts leads to a variety of artifact patterns which are sensitive to the pulsation period and repetition time of the pulse sequence. Numer ical simulations of these effects were found to be in good agreement w ith experimental images of an elastic model of a human carotid artery under simulated physiological conditions and with images of two human subjects.