Phase-contrast with interleaved undersampled projections

NIR phase-contrast techniques provide velocity-sensitive angiograms and qua ntitative flow measurements but require long scan times. Recently it has be en shown that undersampled projection reconstruction can acquire higher res olution per unit time than Fourier techniques with acceptable artifacts whe n used in contrast-enhanced MR angiography, Undersampled projection reconst ruction has similar potential for phase-contrast acquisitions. Flow sensiti zation gradients are used with projection trajectories to acquire velocity- dependent phase information. An acquisition scheme that acquires three flow encoding directions on three sets of angular-interleaved projections is in troduced. Depending on the resolution, acquisition times for 3D datasets ca n decrease by factors of two to four. (C) 2000 Wiley-Liss, Inc.