Research On Key Technologies Of Computer-aided Surgical Planning And Navigation System Based On Augmented Reality And Its Experiments

With the continuous development of information technology and digital medicine,computer-aided surgery has become the trend of a new generation of clinical surgeries.It aims to improve surgical precision,reduce surgical risks and achieve accurate and minimally invasive treatment.The surgical planning and navigation technologies are the research focuses in the field of computer-aided surgery and have been widely used in clinical surgeries in recent years.However,currently surgical navigation systems at home and abroad are only suitable for the normalized surgical operations such as the needle biopsy,cutting and drilling.In fact,in clinical practices,surgeons need to determine how the precise positioning,placement and reposition of objects such as 3D-printed patient-specific implants and loosed bone grafts can be ensured according to preoperative planning.Moreover,most of current surgical navigation systems still have shortcomings such as poor visualization and inadequate operational continuity.For this reason,the Augmented Reality(AR)is introduced which is the cutting-edge technology in the world.Combining AR with surgical planning and navigation technologies,the surgical navigation system based on augmented reality has been developed in this study so that the above-mentioned difficulties are effectively solved.The main contents are as follows:1.On the basis of the Ray Casting algorithm,OpenGL's GPU-based Programmable Pipeline is used to realize the highly effective,fast,real-time and high quality 3D rendering.The virtual clipping of the 3D model along any trajectory is studied.The contour line generation algorithm is adopted to obtain the contours of clipped sections of the model.The Ear Clipping algorithm is performed to ensure the continuity of the closure of the clipped model.The development of the preoperative planning system targeted at clinical oral and maxillofacial surgeries and orthopedic surgeries is completed.The preoperative planning system is also integrated with our independently developed intelligent design system for patient-specific surgical template and proved to be practical through clinical application.2.The calibration algorithms of the pivot,axis and surface for surgical instruments in the navigation system are proposed.Key technologies such as the spatial registration and real-time interactive 2D/3D navigation are realized.The sequence diagram of timing collaboration based on UML is adopted to ensure good real time performance of the navigation system.Based on the system architecture of 3D Slicer,a globally known open source software platform for medical image computing and visualization,core functions of the independently developed navigation system are integrated with 3D Slicer as an extension module.The hardware,software and prototype of the surgical navigation system are successfully developed,and the precision validation device is designed and manufactured for the system.The results of the phantom and cadaver experiments show that the precision can meet the requirements of clinical surgeries.3.The calibration method for patient-specific implants and loosed bone grafts are proposed.Point-based or surface matching registration algorithm is used to determine their spatial transformation matrices under the reference coordinate system.Then,the real-time tracking and visualization of patientspecific implants and loosed bone grafts are realized during the surgical operation according to the registration chain and coordinate transformation relations of the navigation system.The phantom experiments show that the overall mean error is 2.61±1.1mm when the surgeon places implants by hands based on experience while the mean error is 0.70±0.27 mm when the system is used.In addition,the pelvic tumor resection and limb-salvage reconstruction have successfully completed with the system in clinical experiment.Post-operative results prove that the system provides strong guarantee for the precise resection of bone tumors and the accurate placement of patient-specific implants.4.The optical photogrammetry calibration algorithm is proposed.Spatial transformation relations are established between the reference coordinate system of the head-mounted display(HMD)and the coordinate system of patients.Preoperatively planned virtual image information,realtime navigation information,and real operation scenes are integrated together in the optical see-through head-mounted display worn by a surgeon and real time matching is guaranteed.Results of the precision validation for the system show the mean distance error of the target points is 1.04±0.09 mm and the mean angle error of axial holes is 1.07±0.05°,sufficient to meet clinical requirements.Furthermore,the cadaver experiment of the percutaneous implantation of sacroiliac joint screws verifies the reliability of the system.This study investigates and develops the surgical planning and navigation system based on augmented reality,and an integrated digital platform is established.As a result,the image-guided precise operations such as the removal,placement and reposition of the patient-specific implant and the loosed bone graft are achieved.Particularly,the adoption of the augmented reality technology solves the common defects of traditional surgical navigation systems,like poor integration of the virtual and the real and inadequate real-time interactivity,thus providing a new option for characteristic,digital,precise and minimally invasive surgeries in China.