I would like to suggest you some useful links:

http://www.floriansteinke.net/papers/CVPR2009.pdf

Article Lecture Notes in Computer Science

https://link.springer.com/content/pdf/10.1007/11566489_32.pdf

Conference Paper A new similarity measure for multi-modal image registration

I will refer you to the following links:

https://ieeexplore.ieee.org/document/5635425

Article Evaluation of Image Registration Accuracy for Tumor and Orga...

Article Evaluating Similarity Measures for Brain Image Registration

@Muhammad Ali @Sajjad Afrakhteh

Thanks for your helpful replies

Several years ago, some researchers at my institute introduced another similarity measure called Normalized gradient field (NGF). Since then, we are using mainly the NGF similarity measure, because it performs best. Even for registration of images with the same image modality, NGF can perform better than SSD.

You can find more information about NGF, for example in this publication:

Conference Paper A fully parallel algorithm for multimodal image registration...

@sonja

It was useful, thank you