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Multi-Resolution Techniques

To both speed up the optimisation process and to avoid local minima, most currently used registration methods employ some form of multi-resolution optimisation. That is, a sequence of image pairs, at progressively larger spatial scales are created from the initial pair of images: $ (I^r, I^f)$. The images at larger scales are subsampled versions (often with pre-blurring) of the original high-resolution images, and so contain fewer voxels which means that evaluating the cost function requires less computation. In addition, as only gross features of the images remain at these large scales, it is hoped that there will be fewer local minima for the optimisation to ``get stuck'' in.

Peter Bannister 2002-05-03