Shen Guofang

A pilot application of image-guided navigation system in mandibular angle reduction surgery

Mandibular angle reduction is the one of the most popular methods applied toward correcting the prominent mandibular angle(PMA) in Asian countries. The purpose of this study is to apply a computer-aided surgical 3D planning and image-guided navigation system (Navi-CMFS) in mandibular angle reduction surgery, aiming at improving the surgical accuracy, minimizing surgical risks and optimizing clinical results.

An integrated surgical planning and virtual training system using a force feedback haptic device for dental implant surgery

The application of dental implants proposes a successful treatment both partially and fully edentulous patients. However, the placement of implants is not without risk due to anatomically complex operation sites in the cranio-maxillofacial region. Therefore, in the field of oral implantology, there is a trend towards computer-aided implant surgery. In this study, an integrated surgical planning and virtual training system is presented. With the introduction of DLL (Dynamic Link Libraries) and some well-known free, open source software libraries such as VTK, ITK, and QT, a modular software named CAPPOIS (Computer Assisted Preoperative Planning for Oral Implant Surgery) was developed for preoperative planning, including medical image importing, image segmentation and 3D-Reconstruction, 2D/3D geometrical measurements, optimization design of the position and orientation of oral implants, etc. Then, the following virtual surgical training system is developed based on the force feedback haptic device, i.e., Omega.3, and the software toolkit of CHAI3D. With the use of this system, the resulting data of the preoperative planning can be transferred, and surgical simulation of the plan can be vividly realized. In this way, the surgeon can grasp the feel of osteotomy procedure, gain experience and therefore improve his skills during the actual dental implant surgery. This pilot study proves helpful for the inexperienced surgeons; however, more clinical cases will be conducted to demonstrate its feasibility and reliability.

Simulation and Evaluation of a Bone Sawing Procedure for Orthognathic Surgery Based on an Experimental Force Model

Bone sawing is widely used in orthognathic surgery to correct maxillary deformities. Successful execution of bone sawing requires a high level of dexterity and experience. A virtual reality (VR) surgical simulator can provide a safe, cost-effective, and repeatable training method. In this study, we developed a VR training simulator with haptic functions to simulate bone-sawing force, which was generated by the experimental force model. Ten human skulls were obtained in this study for the determination of surgical bone-sawing force. Using a 5-DOF machining center and a micro-reciprocating saw, bone specimens with different bone density were sawed at different feed rates (20, 40, and 60 mm/min) and spindle speeds (9800, 11,200 and 12,600 cycles per minute). The sawing forces were recorded with a piezoelectric dynamometer and a signal acquisition system. Linear correlation analysis of all experimental data indicates that there were significant positive linear correlations between bone-sawing force and bone density and tool feed rate and a moderate negative linear correlation with tool spindle rate. By performing multiple regression analysis, the prediction models for the bone-sawing procedure were determined. By employing Omega.6 as a haptic device, a medical simulator for the Lefort I osteotomy was developed based on an experimental force model. Comparison of the force-time curve acquired through experiments and the curve computed from the simulator indicate that the obtained forces based on the experimental force model and the acquired data had the same trend for the bone-sawing procedure of orthognathic surgery.

Development and Testing of a Visuo-Haptic Surgical Training Simulator for Orthognathic Surgery

Visuo-haptic medical training simulator offered a safe, repeatable and cost-effective alternative to traditional surgeries in improving and assessing the surgeons’ skills. In this research, we developed a visuo-haptic surgical training simulator for bone sawing procedures to provide a basically realistic training environment for bone removal processes in orthognathic surgery. The voxel-based model was constructed using computed tomography (CT) images, and the virtual tools were built through reverse engineering. The multi-point collision detection method was applied for haptic rendering to test the 3D relationship between the virtual tool and the bone voxels. By employing Omega.6 as the haptic device and Display300 as the 3D stereo display, a surgical training simulator with haptic functions and virtual reality environment for orthognathic surgery was realized and basic bone sawing procedures were simulated. The haptic forces computed from the simulator were tested by comparing with the real machining forces obtained from the experiments on fresh human bones. Comparison indicated that the computed forces and the acquired data had the same trend for the bonesawing procedure.