Volumetric deformable face models for cranio-facial reconstruction

In forensic cranio-facial reconstruction, facial features of an unknown individual are estimated from an unidentified skull, based on a mixture of experimentally obtained guidelines on the relationship between soft tissues and the underlying skeleton. In this paper, we investigate the possibility of using full 3-D cross-sectional CT images for establishing a reference database of densely sampled distances between the external surfaces of the skull and skin for automated cranio-facial reconstruction. For each CT image in the reference database, the hard tissue (skull) and extra-cranial soft tissue (skin) volumes are segmented and transformed into signed distance transform (sDT) maps. A simplified procedure for cranio-facial reconstruction was implemented, by warping all reference skull sDT maps to the target skull sDT. These warps are subsequently applied to the reference skin sDT maps and the zero level set of their arithmetic average is defined as the reconstructed target skin surface. Initial results are shown to proof the validity of the concept, but further refinement of the procedures involved and a qualitative validation are required.