The effect of motion on a voxel depends not only on the detected motion but also on the location and size of that voxel (e.g., rotation around the center of a voxel has a smaller effect than rotation by the same angle around a point outside the voxel). To quantify this effect, binary masks of the prescribed voxel volumes were generated in the space of the FSE images. The aforementioned difference transformation was then applied to each prescribed voxel mask in FSE space, yielding a reformatted voxel mask, also in FSE space, which represented voxel placement for acquisition. The overlap of prescribed and acquired voxel locations was then computed and expressed in percent of the voxel volume. When there was no motion detected, the difference transformation was the identity transformation, both voxel masks were identical, and overlap 100%.
