We define a methodology for aligning multiple, three-dimensional, magnetic-resonance observations of the human brain over six degrees of freedom. The observations may be taken with disparate resolutions, pulse sequences, and orientations. The alignment method is a practical combination of off-line and interactive computation. An off-line computation first automatically performs a robust surface extraction from each observation. Second, an operator executes interactively on a graphics workstation to produce the alignment. For our experiments, we were able to complete both alignment tasks interactively, due to the quick execution of our implementation of the off-line computation on a highly-parallel supercomputer. To assess accuracy of an alignment, we also propose a consistency measure.
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