Deformable registration with spatially varying degrees of freedom constraints

Intra-subject deformable registration applications, such as longitudinal analysis and multi-modal imaging, use a high degree freedom deformation to accurately align soft tissue. However, smoothness constraints applied to the deformation and insufficient 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 deformation.