A CT-Imaging, CAD-Based Bone Reconstruction

In the recent years, the total hip arthroplasty (THA) as the efficient treatment has been broadly applied in the clinical field, however the match degree of prosthesis shape to the femoral medullar cavity will directly affect the longevity of the prosthesis. Prolong the longevity is the key to prostheses design. Due to the diversity in different person's femoral shape, the common commercial prostheses can't meet need of match degree, therefore the stability of the prostheses cannot be guaranteed as the time passes. Through the CAD/CAM assisted custom design, the life expectancy of prostheses will be highly improved and the loosing of the prostheses will be effectively avoided.Based on the background, this subject is developed supported by the science committee of Tianjin. This paper discusses the image processing and the methods of 3D reconstruction based on the image processing theory and computer graphics. On the condition, an image processing system is built up and the 3D reconstruction of femur is achieved in virtue of Pro/Engineer, a kind of 3D CAD software.Firstly, analyzes the CT picture characteristic, and establishes the CT image processing algorithm. Under the VC++6.0 environment, the system is established in view of the CT image characteristic, which can read the slice image, carry on the geometry processing of translation, enlargement and reduction, and the function of filtering, binarization and contour extraction.These operations are prepared for the computer three dimensional reconstruction, which make the CT image processing more convenient, systematic and accurate, and provided precise datas for model construction.Then under the Pro/Engineer environment, in the light of theory of 3D reconstruction, the data point of interface file can be fitted into spline curves. Afterward, the spline curves can be faired and optimized. The femoral surface is achieved by the function of surface modeling. In this process, the method of combining the growing rale with parallel method in v control direction is provided. Finally, the femoral surface is translated into an entity and the work of 3D reconstruction of femur is finished. In order to check up the error of this 3D model, we choose another method to build entity, which is translated from thousands of point-coordinates by 3D measuring tool. It gives a satisfied effect. At the end of the paper, machining method is discussed.