Simultaneous surface and volumetric registration using harmonic maps

Inter-subject analysis of anatomical and functional brain imaging data requires the images to be registered to a common coordinate system in which anatomical features are aligned. Intensity-based volume registration methods can align subcortical structures well, but the variability in sulcal folding patterns typically results in misalignment of the cortical surface. Conversely, surface-based registration using sulcal features can produce excellent cortical alignment but the mapping between brains is restricted to the cortical surface. Here we describe a method for volumetric registration that also produces a one-to-one point correspondence between cortical surfaces. This is achieved by first parameterizing and aligning the cortical surfaces. We then use a constrained harmonic mapping to define a volumetric correspondence between brains. Finally, the correspondence is refined using an intensity-based warp. We evaluate the performance of our proposed method in terms of the inter-subject alignment of expert-labeled sub-cortical structures after registration.