4D Gradient Based Phase Unwrapping for PC-MR Flow Data

Michael Loecher¹, Kevin Johnson¹, Benjamin Landgraf¹, Oliver Wieben^1,2

4D PC MRI has emerged as a promising approach for hemodynamic evaluation of larger vascular territories. One of the major problems associated with volumetric phase contrast MRI is the large dynamic range of velocities of interest and the potential risk of velocity aliasing in areas of higher velocities. This work describes an algorithm that minimizes local gradients in 4 dimensions within vessels to detect and correct phase wrapped voxels. This method is strengthened by the use of PC-VIPR, allowing for small voxel sizes and high temporal resolution. The algorithm is generally successful as long as wrapping stays below certain levels.