Because of the accuracy required in a neurosurgical procedure, tracking intra-operative deformations is a challenging task. Furthermore, the clinical demand for fast non rigid registration will have to be met in a very near future. In this paper, we propose a patient-specific biomechanical model based on block-matching in order to register two MR images of the same patient with a parallel implementation. Compared to other intra-operative registration techniques, this method combines a

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... ic mechanical regularization with a correlation-based iconic energy term. We first shortly present the theoretical aspects of our method (more detailed in [9] ). Then we describe in more details the parallel implementation of the algorithm. Finally we present a retrospective registration study made of four pre/post operative MRI pairs.