Three-dimensional motion tracking with volumetric phase contrast MR velocity imaging.

Motion tracking based on single-slice cine-phase contrast magnetic resonance imaging data has limitations. In the presence of nontrivial three-dimensional motion and deformation, volumetric data are necessary for accurate reconstruction of material point trajectories. A three-dimensional Fourier tracking method that uses volumetric data for motion tracking is presented. The method reconstructs a material point trajectory by computing its various harmonics. For any given temporal sampling rate, a frequency domain perspective of the tracking problem indicates that the method is accurate in estimating all reconstructible harmonics of a trajectory. The algorithm incorporates an intra-voxel linear spatial model into the integration to address potential tracking performance degradation due to possibly reduced spatial resolution, which may be most relevant in the slice direction (z) if the volumetric data are obtained as multiple two-dimensional slices. The tracking method was evaluated on computer-generated data sets that simulated various motion patterns. The method was also tested with two sets of in vitro data obtained using a phantom, one acquired as multiple two-dimensional slices and the other using a three-dimensional sequence capable of higher spatial resolution in the z direction. These studies demonstrated that the algorithm can achieve high sub-voxel tracking accuracy.