Automatic reconstruction of 3D geometry using projections and a geometric prior model

A method has been developed to reconstruct 3D surfaces from two orthogonal X-ray projections. A 3D geometrical prior model, composed of triangulated surfaces, is deformed according to contours segmented from projection images. The contours are segmented by a new method based on free-form deformation. First, virtual X-ray images of the prior model are constructed by simulating real X-ray imaging, Thereafter, the contours segmented from the virtual projections are elastically matched with patient data. Next, the produced 2D vectors are back-projected onto the surface of the prior model and the prior model is deformed using the back-projected vectors with shape-based interpolation. The accuracy of the method is validated by it data set, containing 20 cases. The method is applied to reconstruct thorax and lung surfaces. The average matching error is about 1.2 voxels, corresponding to 5 mm.