Intervention-based multidimensional phase unwrapping using recursive orthogonal referring

We present a new intervention-based phase unwrapping algorithm, which solves the inherent integration-path-dependent problem (typically resulting in streaks), by using a 2D recursive orthogonal referring (PUROR) approach. The streaks were removed by three consecutive procedures: intra-image phase unwrapping, inter-image cross-referring a good-strip, and cross-referring line segments. The application of these procedures results in streak-free 2D phase images. The phase inconsistencies across slices in a 3D image were removed using a hybrid 3D PUROR algorithm: the two step approach involves stacking the individual slices, by using the mean phase values of each slice, then applying the 2D PUROR algorithm to reformatted 2D images that include the slice direction. The described approach was tested with in vivo multislice phase images acquired in the axial, sagittal, and coronal orientation. The results of the unwrapped phase volume recovered using the PUROR algorithm have equivalent quality to that achieved by using established methods, but the PUROR algorithm is about two orders of magnitude faster (between 1 and 5 s per 256 x 256 slice; independent of slice orientation and echo time). Magn Reson Med, 2012. (c) 2012 Wiley Periodicals, Inc.