Joint learning of appearance and transformation for predicting brain MR image registration.

We propose a new approach to register the subject image with the template by leveraging a set of training images that are pre-aligned to the template. We argue that, if voxels in the subject and the training images share similar local appearances and transformations, they may have common correspondence in the template. In this way, we learn the sparse representation of certain subject voxel to reveal several similar candidate voxels in the training images. Each selected training candidate can bridge the correspondence from the subject voxel to the template space, thus predicting the transformation associated with the subject voxel at the confidence level that relates to the learned sparse coefficient. Following this strategy, we first predict transformations at selected key points, and retain multiple predictions on each key point (instead of allowing a single correspondence only). Then, by utilizing all key points and their predictions with varying confidences, we adaptively reconstruct the dense transformation field that warps the subject to the template. For robustness and computation speed, we embed the prediction-reconstruction protocol above into a multi-resolution hierarchy. In the final, we efficiently refine our estimated transformation field via existing registration method. We apply our method to registering brain MR images, and conclude that the proposed method is competent to improve registration performances in terms of time cost as well as accuracy.