An Improved Quality Guided Phase Unwrapping Method and Its Applications to MRI

An improved method of quality guided phase unwrapping (QGPU) is proposed in this work. It extracts the quality map via a median filtered phase derivative variance (MFPDV) that applies a two-dimensional median filter on the phase derivative variance (PDV) map, in order to reduce the effect of noise in the background area. In addition, we employed the Indexed Interwoven Linked List (I2L2) structure to store the orderly adjoin list more efficiently and the Two Section Guided Strategy (TSGS) to reduce comparison frequency. The experiments demonstrate that the normalized L-1 norm of MFPDV of a brain MR image is only 0.0827, less than that of PDV method at 0.0923. Besides, the computation time of QGPU with I2L2 technique is only 30% of that with sequence structure, and the computation time of QGPU with TSGS is only 65% of that without TSGS. In total, the proposed MFPDV upwrap phase images better than conventional PDV map, and I2L2 and TSGS are efficient strategies to reduce computation time.