Study On Key Technologies Of Cutting Deformation Of Liver Model Based On Augmented Reality

In current liver surgery,doctors face the problem of invisible liver tissue during the operation.In traditional open liver surgery,doctors use the preoperative CT and intraoperative ultrasound to roughly locate tumors and other lesions in the liver.The preoperative CT and intraoperative ultrasound are two-dimensional information,and there is a problem of mismatch of information between the preoperative CT and the intraoperative surgery.The poor quality of the intraoperative ultrasound imaging is difficult to accurately locate the lesion.Therefore,using augmented reality technology to assist doctors in liver surgery has important practical significance.This article focuses on the key technologies of liver cutting with the aid of augmented reality,and aims to provide doctors with additional surgical information during liver surgery to help doctors complete the surgery better and faster.First,the modular design of the liver cutting program based on augmented reality is performed,and the functions of each module are described in detail.The models used for surgical assistance were mainly reconstructed by preoperative CT.The 3D reconstruction technology based on CT was studied,and a 3D mesh model of the liver was obtained through CT reconstruction of real patients.For open simulation surgery,we chose to use static video to display augmented reality images,and at the same time tracked and registered surgical instruments and liver using a marker-based method,which realized the basic functions of augmented reality.The change of topological structure during liver model cutting was studied.For the problem that needs to obtain the precise cutting point,a method similar to ray casting is used to calculate the precise position of the line and surface intersection to obtain the cutting position.In order to avoid the problem that the number of triangular elements in the model is increased during the cutting process,the calculation amount is increased,and the moving vertex method is used to cut the surface mesh.Aiming at the problem that the moving vertex method is easy to generate degenerate triangles,the Delaunay criterion and LOP method are used to optimize the mesh near the moving vertex to eliminate the degenerate triangles.Aiming at the problem that there is no cutting surface caused by the lack of realism after the patch is split,a method for constructing the cutting surface of a multi-row unit is proposed,which can form a cutting surface that fits the cutting track and depth.The physical model of the liver model deformed by gravity was studied.A simple analysis of the biomechanical characteristics of the liver was performed,and a physical model of liver deformation was established based on the mass spring theory.A general program for converting triangular mesh models to tetrahedral models was written using QT in conjunction with Tetgen.The output liver tetrahedron model was connected using Voigt components to simulate the deformation of the liver under gravity.Aiming at the problem that the liver model has a large amount of data and slow calculations,the program is accelerated using GPGPU acceleration technology,which greatly improves the refresh rate and real-time performance of the program.Finally,an experimental platform for liver cutting based on augmented reality was designed and constructed.The platform has been used for experimental verification of the above key technologies,including accuracy experiments of augmented reality modules,deformation accuracy experiments of liver models using mass spring under gravity,and cutting accuracy experiments,and the completion of cutting around the lesion with the assistance of augmented reality experiment.