图像配准中最有挑战的是图像包含不同的形态特征。这种情况下，直接比较灰度水平的方法是不可行的。交互信息的评估很好地克服了多模态配准的困难。-Some of the most challenging cases of

image registration arise when images of

different modal-ities are involved. In such cases, metrics based on direct comparison of gray levels are not applicable. It has been extensively

shown that metrics based on the evaluation of mutual infor-mation are well suited for overcoming the difficulties of multi-modality registration.