Elastic material model mismatch effects in deformable motion estimation

Deformable motion models are useful for analysis of dynamic datasets exhibiting non-rigid motion, as in gated cardiac PET. The authors employ an algorithm that obtains a vector field to describe the relative motion of each voxel between two data sets. The estimation is based on a two-component cost function: an image matching component, and a motion field smoothness component. An important aspect of obtaining an accurate motion field estimate is properly balancing the weight between the two cost components. The authors show that by using a material elastic model inspired by continuum mechanics, an intuitive interpretation of the weighting factors for the smoothness constraint may be obtained. Further, they show that mismatches between actual material elastic parameters and those used by the estimation algorithm can lead to greater estimation error. Results are validated using an ellipsoidal phantom simulating compressible and incompressible deformations.