Skerl Darko, Likar Bostjan, Fitzpatrick J Michael, Pernus Franjo
Faculty of Electrical Engineering, University of Ljubljana, Ljubljana, Slovenia.
Phys Med Biol. 2007 Sep 21;52(18):5587-601. doi: 10.1088/0031-9155/52/18/008. Epub 2007 Sep 3.
Image registrations that are based on similarity measures simply adjust the parameters of an appropriate spatial transformation model until the similarity measure reaches an optimum. The numerous similarity measures that have been proposed in the past are differently sensitive to imaging modality, image content and differences in the image content, selection of the floating and target image, partial image overlap, etc. In this paper, we evaluate and compare 12 similarity measures for the rigid registration. To study the impact of different imaging modalities on the behavior of similarity measures, we have used 16 CT/MR and 6 PET/MR image pairs with known 'gold standard' registrations. The results for the PET/MR registration and for the registration of CT to both rectified and unrectified MR images indicate that mutual information, normalized mutual information and the entropy correlation coefficient are the most accurate similarity measures and have the smallest risk of being trapped in a local optimum. The results of an experiment on the impact of exchanging the floating and target image indicate that, especially in MR/PET registrations, the behavior of some similarity measures, such as mutual information, significantly depends on which image is the floating and which is the target.
基于相似性度量的图像配准只是调整适当空间变换模型的参数，直到相似性度量达到最优值。过去提出的众多相似性度量对成像模态、图像内容以及图像内容差异、浮动图像和目标图像的选择、部分图像重叠等具有不同的敏感性。在本文中，我们评估并比较了用于刚体配准的12种相似性度量。为了研究不同成像模态对相似性度量行为的影响，我们使用了16对具有已知“金标准”配准的CT/MR图像对和6对PET/MR图像对。PET/MR配准以及CT与校正和未校正MR图像配准的结果表明，互信息、归一化互信息和熵相关系数是最准确的相似性度量，并且陷入局部最优的风险最小。关于交换浮动图像和目标图像的影响的实验结果表明，特别是在MR/PET配准中，一些相似性度量（如互信息）的行为很大程度上取决于哪幅图像是浮动图像，哪幅是目标图像。
