Novel method to correct displacement profile images and calculate flow vector fields using saturation-tagging MR...

Saturation-tagging Magnetic Resonance (MR) imaging provides a simple and robust means to directly visualize displacement profiles within fluid flow fields. Although useful for velocity quantitation as well as for qualitative depiction of flow patterns in certain well-defined flow fields, the technique is prone to distortions due to oblique flow (misregistration artifact) and ambiguity of fluid vector trajectories in complex flow situations. A novel method is proposed whereby two images are acquired, differing in the temporal position of the phase encoding gradient. Theoretical analysis shows that from the paired images, distortion of the two-dimensional displacement profile can be corrected and fluid velocity vectors extracted, even if the flow directions are unknown. In the simpler case of flow oblique to the gradient principal axes, but with a known trajectory, only one image is necessary to correct the displacement profile distortion and extract the velocity information. MRI experiments in a straight tube model have been carried out to evaluate the feasibility of this method. Good agreement is achieved between the results from MR imaging and those predicted via computer simulation.