Research On Deformation Technique Of Human Soft Tissue In Virtual Surgery

Owing to growing needs for modern medicine, Virtual Surgery, an important application in this field, is formed by the combination of virtual reality technology and surgery. A virtual surgery system provides users with an exact reproduction of surgical scene. It can be applied to preoperative planning, intraoperative navigation, surgeon training, etc. Virtual surgery plays an important role in extending surgery training and complicated operation. As a result of inevitably touching many soft tissues for doctors in surgical operations, the biological simulation of human soft tissue deformation becomes one of the key technologies in virtual surgery, and it severely restricts the development of virtual surgery as well.In this paper, a soft tissue deformation simulation system based on force feedback is designed and established. The implemented virtual surgery system uses real medical images of patients as the original data, and has the function of locating focal lesions.Firstly, based on typical elements of a force feedback virtual surgery system, hardware and software components, structure of system framework and software modules are designed for the implemented system.Secondly, the geometric model of the patient's soft tissues in the implemented system is established via recognizing the preprocessed data file from the original medical image. In addition, a sequence of the same patient's CT images in DICOM format is reconstructed in three-dimensions which plays an assistant role of preoperative observation.Thirdly, a special data structure -- the adjacency list of edges is designed and combined with the geometric model and Mass-Spring System (MSS) principle that leads to the establishment of the physical model of soft tissues. Then, the mechanical properties of soft tissue deformation is analyzed and solved by the 4th order Runge-Kutta Method. At last, human soft tissue deformation simulation is achieved on the basis of the above contents and the principle of force propagation model.Finally, a search algorithm of boundary of focal lesion is designed based on the adjacency list of edges. Human soft tissue deformation simulation with the function of focal lesions location and force feedback is realized. The location and size of focal lesions are changeable.The implemented system applies the OpenGL graphics standard to establish the three-dimensional surface models of human soft tissues and organs, uses the PHANToM Omni as the haptic interaction device and employs MSS and force propagation model to form soft tissue deformation model. The experimental results show that the bidirectional force feedback of the system meets the multi-channel interactive requirements, and that the human soft tissue model on the basis of real medical origin and efficient data processing mode well balance the precision and the real-time requirements of the human soft tissue deformation simulation.