Non-linear Registration with the Variable Viscosity Fluid Algorithm

In this paper we classify inhomogeneous non-linear registration algorithms into those of variable data influence, of variable deformability and of variable model type. As examples we introduce three modifications of the viscous fluid registration algorithm: passing a filter over the computed force field, adding boundary conditions onto the velocity field, and re-writing the viscous fluid PDE to accommodate a spatially-varying viscosity field. We demonstrate their application on artificial test data, on pre-/post-operative MR head slices and on MR neck volumes.