Differences in fiber orientations between registered image volumes can be difficult to quantify. Angular errors between diffusion tensor imaging (DTI) volumes are often a combination of image registration errors and fluctuations of diffusion values that are used to determine the fiber orientations. In order to properly quantify the similarity between two images containing fiber orientation information, both displacement and angular fluctuation should be considered. We present a method to quantify fiber orientation similarity between registered images by allowing small pixel displacements in conjunction with minor angle differences. Adjustments to the allowed pixel displacement and degree of angle difference can help identify the major factor contributing to the error of fiber angles. The proposed method can provide a new metric for the evaluation of the fiber orientation difference.
Keywords: Fiber orientation; cardiac fiber; gamma calculation; image registration; magnetic resonance diffusion tensor imaging (MR-DTI); similarity.