Demons registration with local affine adaptive regularization: application to registration of abdominal structures

We present a local affine-based adaptive regularization approach as an alternative to the homogeneous regularization used in Thirion´s demons non-rigid registration algorithm, which does not preserve the deformation field discontinuities related to the independent motion of different organs, as typically occurs during CT and MR imaging of the abdomen and pelvis. By contrast, our method fits local affine transformation to each voxel; identifies the discontinuities between the locally fitted affine transformations; and adaptively smooths the deformation field, while preserving its local affine discontinuities. Experimental results on both synthetic and real CT images demonstrate that our method at once yields a smoother deformation field and preserves registration accuracy.