I have a problem that I can’t think about. I rotate the image with setparameters() function by 1 radian on the Z axis, and then calculate the mutual information value A between the graph and the fixed image. The mutual information value B between the Image without rotation and the fixed image ， the difference of mutual information is not large (less than 0.1). Why is this? The rotation error range of medical images should be ± 1 ° or ± 2 ° I think. Why does the mutual information value not change much after I rotate such a large angle?