Study Of A Liver Virtual Surgery System Based On Voxel And Position Based Dynamics

Virtual surgery system is an important application of VR technology in the medical field,which aims to reproduce real surgery and provide a low-cost,noninvasive,reusable surgical training and assistance platform for medical workers,with broad application prospects and research value.However,given the complexity of the clinical environment,virtual surgery involves the integration of multidisciplinary techniques and is difficult to study.Among them,soft tissue modeling is the core part of virtual surgery,which is the basis of deformation simulation,visual-haptic rendering,cutting simulation and other functions,and has high requirements for real-time,realism and stability.In this context,this thesis aims at a liver virtual surgery system based on voxel and position-based dynamics,and the following studies were conducted:(1)In terms of geometry modeling,this thesis introduces a modeling system based on the organ segmentation cloud platform,which simplifies the complex modeling process into a "one-click" operation on the browser platform,and allows users to reconstruct real organ models for surgical simulation by uploading CT images,improving the practicality and realism of the system.(2)In terms of soft tissue modeling,this thesis proposes a soft tissue modeling method based on voxel and position-based dynamics.The method has good compatibility with specification-random and mass-random geometric models and the soft tissue models constructed can achieve fast,stable and visually credible deformation effects.Meanwhile,on the basis of model characteristics,this thesis proposes a ray-based collision detection and feedback force calculation method based on weighted displacement,which provides theoretical support for the system interaction function.(3)In terms of cutting simulation,this thesis proposes a particle rejectionbased electric knife cutting method and initially constructs a heat conduction model for voxels.Experiments show that the method in this thesis can better simulate the volume removal phenomenon in electric knife cutting,while the cutting effect is more uniform with the deformation effect,which can realize the progressive electric knife cutting simulation with high degree of freedom.In addition,a visualization tool for estimating the residual volume of the liver is designed in this thesis to facilitate the users in planning the cutting path.(4)On the basis of the above research,a liver virtual surgery system is constructed in this thesis.Based on this system,this thesis uses real CT data for the simulation of right hemihepatectomy.Experimental show that this system was highly rated by subjects in terms of user friendliness and organ deformation,while the operational response speed of the system reached the millisecond level and the average running frame rate exceeded the device rendering limit of 90 Hz,which can provide smooth and stable simulation,indicating that the system can be a powerful supplement to conventional surgical training and teaching.