HIGH-PRECISION MR VELOCITY MAPPING BY 3D-FOURIER PHASE ENCODING WITH A SMALL NUMBER OF ENCODING STEPS

The final result of Fourier velocity mapping is a set of images, each representing the spatial distribution of spins at a given velocity. To acquire data in a short time, the number of encoding gradient steps m ust be as small as possible, but this can mean sacrificing velocity re solution. We used interpolation methods to obtain high velocity resolu tion with a small number of encoding steps involving linear interpolat ion from 16 encoding steps or more and zero-filling interpolation from two to eight encoding steps. Velocity measured by interpolated Fourie r-flow encoding agreed well with values obtained using a calibrated ph antom. A simulation of noise on the images of the phantom showed that, for a given acquisition time, increasing number of encoding steps in the Fourier flow encoding gave better precision for velocity measureme nt than did averaging identical signals in phase-mapping methods.