Study On Computer-aided Pedicle Screw Implantation System Based On Interactive Visualization

Posterior pedicle screws fixation is an important means to treat various spinal lesions,but the current modes for surgery program formulation of the therapy cannot adapt to the complicated clinical environment and the needs of high-risk control.Computer-assisted surgeries can achieve accurate surgical simulation and design of surgery programs,thereby improving the accuracy and success rate of the surgeries.Therefore,the reconstruction of high-quality 3D model by means of visualization technology and the design of system with favorable interactive performance to achieve safe and individualized surgical planning are of great research significance and application value.In this paper,in view of the requirements of pedicle screw implantation,around the topic of realization of precise design of individualized surgical programs,in-depth study and investigation were conducted on the image processing algorithm,visualization technology,model interactive simulation technology and rapid prototyping technology involved in the design process of computer-assisted pedicle screw fixation operation,and the following results were obtained:1.In order to meet the analysis needs of three-dimensional assessment of scoliosis,and lay the groundwork for the design of computer-assisted pedicle screw implantation,a spinal bone block separation processing method based on MC algorithm oriented surface rendering was proposed,and in-depth investigation on the three visualization interaction surgical means of the algorithm was conducted.Firstly,the principle and implementation method of MC algorithm were introduced.Secondly,based on the realization process of MC algorithm oriented surface rendering,the cutting way for spine in voxel level was proposed,and rapid coarse segmentation of the target spine was achieved.Finally,the connectivity of the three-dimensional medical volume data was discussed,and the visualization interaction means for pixel erasure was innovatively put forward based on the segmentation labeling technique,with which the non-target tissues in the spatial interosseous of the target spine can be accurately erased,thus realizing the segmentation of spine.2.In order to precisely design the implantation site of pedicle screws and improve the operating performance of model interaction,this paper proposed a new method for screw positioning based on the spatial geometric transformation of contour lines.Through in-depth analysis of the attitude transformation and feature points generation mechanism of the three-dimensional model under the rendering principle,the three-dimensional contour line of the characteristic face was obtained,and optimization processing on the continuity of the contour line was conducted by Prim algorithm;then the contour line was performed spatial geometric transformation and mapped into the two-dimensional space;finally,the two-dimensional contour line was taken as a reference to directly and accurately complete the positioning plan of the pedicle screws.3.In order to further ensure the smooth implementation of the surgery program in clinic and to realize information docking with other CAD systems,a rapid prototyping file interface mode was designed in this paper.Through in-depth study of the rapid prototyping technology,a STL file generation method based on MC algorithm was proposed,with which correct STL files can be output quickly;meanwhile,a STL file read and display mode was designed based on the OpenGL graphic software interface,so as to achieve effective information read and three-dimensional model rendering of STL files.4.Based on the above research,the computer-assisted pedicle screw implantation system based on visualization interaction was designed and developed in this paper.The design thought,overall structure,function module and key technology of the visualization system were introduced in detail.The clinical case tests have demonstrated that this system can meet the intuitive and interactive requirements of the pedicle screw fixation operation and can assist doctors to make precise surgery program design.