Physics-based 3D head model reconstruction from cephalograms for medical application

Engineering techniques are being vigorously utilized in the medical sector. Examples are the visualization of human body measurements such as CT and MRI by computer graphics, and the prediction of the results of surgery by computer simulation. This paper discusses a system in which a cephalogram is constructed on the basis of anatomical knowledge, and the change in the 3D facial shape after facial surgery, especially corrective surgery on the jaw, is predicted. The proposed model has a layered structure composed of skeleton, muscle, and skin, and can use physical calculations to generate dynamically the modification of the facial surface accompanying the motion of muscle and skeleton. Using this cephalogram as the standard model, the facial surface and the skeleton shape are modified on the basis of 3D coordinate data on the measurement points obtained from two x-ray normalized images taken from the front and the side, and the head model for the individual is constructed. The change in shape of the facial surface when bone is moved following the actual surgical procedure is predicted in 3D. In the prediction experiment, a head model was constructed from the x-ray normalization images of the patient before surgery, and the surgical procedure was simulated. The prediction result was compared with the actual results and evaluated, and demonstrated the effectiveness of the proposed method.