Deformable registration with spatially varying degrees of freedom constraints

Intrasubject deformable registration applications, such as lon-gitudinal analysis and multimodal imaging, use a high degree freedom deformation to accurately align soft tissue. However, smoothness constraints applied to the deformation and insuf-ficient degrees of freedom in the deformation may distort the more rigid tissue types such as bone. In this paper, we present a technique that aligns rigid structures using rigid constraints while aligning soft tissue with a high degree of freedom de-formation. Index Terms — Deformable image registration, optical flow, anatomy-specific constraints, volume preservation