Validation of cine phase-contrast MR imaging for motion analysis.

The accuracy of cine phase-contrast magnetic resonance (MR) imaging for motion analysis was evaluated. By using a rotating phantom and postprocessing algorithm for phase tracking, errors arising during data acquisition were identified and compensation methods were developed. A spatially varying background phase offset in the velocity images was found to be due to eddy current-induced fields. The magnitude of the offset was in the range of 0-20 cm/sec, which is of the same order of magnitude as cardiac contractile velocities. Background offset is thus an important source of error in tracking cardiac motion. Study of different tracking algorithms revealed the need for an integration scheme using motion terms higher than velocity. Also, considerable improvement in the accuracy and stability of the predicted trajectories was obtained by averaging the trajectories proceeding both forward and backward in time from the starting point. With the algorithm developed, the motion of the phantom was tracked through a complete rotation of the phantom to an accuracy of 2 pixels.