The Research On Key Algorithms Of Customized Surgical Template Design Software And System Implementation Based On 3D Printing Technology

Aiming at communicating the highly precise preoperative planning onto the surgical site intraoperatively, customized surgical template has been widely utilized as an effective solution in various surgical interventions. In China, there are two common methods of surgical template design, including foreign commercial solutions and designing with CAD software. However, they both have disadvantages. The former demands a high cost and a relatively long delivery time. Besides, in most cases, the surgeons cannot participate in the template design process. As for the latter, because surgeons are not familiar with CAD software, the complex procedures of template design are usually accomplished by engineers. To solve these problems, this dissertation presents a generalized framework of customized surgical template design based on 3D printing technology. It is a semi-automatic computer-aided design method. The user just needs to position control points on the reconstructed mesh, import axes of implants or medical screws from preoperative planning results, and input related parameters. Then the customized surgical template will be generated automatically.Several key algorithms were studied, including mesh segmentation, offset surface generation, surface filling with specified boundary, Boolean Operation, etc. The main workflow of this method goes as follows. Firstly, mesh segmentation with signed scalar of vertex is utilized to partition the inner surface from the input reconstructed mesh based on the point loop indicated by the user. The offset surface of the inner surface is obtained by extracting an isoline from the distance field of the inner surface based on the thickness of template, and then it is segmented to generate the outer surface. Ruled surface is employed to connect inner and outer surfaces so that the initial template is finished. Here it is transferred to shortest path problem in a directed weighting graph, and solved with a label setting algorithm. Finally, cylinders for drilling tubes are generated according to the preoperative planning results and user defined parameters. With the Boolean Operation algorithm this dissertation described, drilling tubes are added to the initial template. Then the final template model will be exported in STL format, which can be used for 3D printing directly.Using these algorithms, the template design software was developed with Microsoft Visual Studio 2008. Two famous open source toolkits, namely Qt and VTK were involved. It was also integrated into a preoperative planning software. With the user-friendly interface, a customized template can be designed according to the reconstructed mesh and preoperative planning conveniently. It was applied to template design for various surgeries. Software running efficiency and the related parameters were analyzed. Accordingly, the functionality, efficiency and generality of our method were demonstrated.