COMBINED ANALYSIS OF SPATIAL AND VELOCITY DISPLACEMENT ARTIFACTS IN PHASE-CONTRAST MEASUREMENTS OF COMPLEX FLOWS

MR phase contrast (PC) velocity imaging is a promising tool for quanti fying blood now velocity in vivo. PC velocity imaging is, however, sus ceptible to artifacts that result from the displacement of spins durin g the finite duration pulse sequences. Such displacement artifacts can lead to errors in velocity measurements, especially in the presence o f oblique and accelerating flows, which are common throughout the card iovascular system. By tracking particles (representing spins) through a computed velocity held, and assuming that spatial and velocity encod ings occur at discrete times during the pulse sequence, we simulate th e separate and combined effects of oblique and acceleration artifacts on PC velocity images. We demonstrate, both by simulation and MR measu rement, the errors associated with such artifacts in PC velocity measu rements in a representative now geometry. Using example particle traje ctories, we provide a fluid dynamic basis for characteristic phase-vel ocity image distortions that can arise when imaging complex, physiolog ically relevant flows.