Nonsubtractive spiral phase contrast velocity imaging

Phase contrast velocity imaging is a standard method for accurate in vivo f low measurement. One drawback, however, is that it lengthens the scan time (or reduces the achievable temporal resolution) because one has to acquire two or more images with different flow sensitivities and subtract their pha ses to produce the final velocity image. Without this step, non-flow-relate d phase variations will give rise to an erroneous, spatially varying backgr ound velocity. In this paper, we introduce a novel phase contrast velocity imaging technique that requires the acquisition of only a single image. The idea is to estimate the background phase variation from the flow-encoded i mage itself and then have it removed, leaving only the flow-related phase t o generate a corrected flow image. This technique is sensitive to flow In o ne direction and requires 50% less scan time than conventional phase contra st velocity imaging. Phantom and in vivo results were obtained and compared with those of the conventional method, demonstrating the new method's effe ctiveness in measuring flow in various vessels of the body. Magn Reson Med 42:704-713, 1999. (C) 1999 Wiley-Liss, Inc.