2D/3D deformable registration using a hybrid atlas.

Statistical atlases built by point distribution models (PDMs) using a novel hybrid 3D shape model were used for surface reconstruction. The hybrid shape model removes the need for global scaling in aligning training examples and instance generation, thereby allowing the PDM to capture a wider range of variations. The atlases can be used to reconstruct, or deformably register, the surface model of an object from just two to four 2D x-ray projections of the object. The methods was tested using proximal and distal femurs. Results of simulated projections and fluoroscopic images of cadaver knees show that the new instances can be registered with an accuracy of about 2 mm.