Effects of intravoxel velocity distributions on the complex difference method of phase‐contrast MR angiography

The complex difference method of phase‐contrast MR angiography is affected not only by the degree of velocity encoding applied during the scan but also by the variance of the intravoxel velocity distribution. The reconstructed intensities of voxels with the same average flow rate but different variances of the velocity distribution can differ significantly. Mathematical analysis and scanner phantom experiments confirm this conclusion.