The Development Of Surgical Navigation Systems Based On Electromagnetic Tracking

With the continuous development of computer technology,surgical navigation systems have been widely applied in clinical surgeries.However,the surgical navigation systems in China are mainly based on optical tracking and their application scenario is limited at present.And the optical navigation systems have the strong possibility to be affected by the disruption to the line of sight.As a result,it may result in the invisibility of the trackers and reduce the continuity of surgery operations.However,doctors have to face and overcome many challenges such as patients’forced positions,high surgery accuracy needed and long operation time.This paper combined the advantages with dynamic navigation and electromagnetic(EM)positioning and developed the image-guided surgery navigation systems based on EM tracking.And the main researches are as follows:(1)A registration algorithm for targeted holes was proposed.And it was used to compute the registration matrix of the distal screw holes by assembling the standard nylon screws,nuts and target interlocking intramedullary nail.A weighted optimization registration algorithm is proposed based on the famous open source software VTK(The Visualization Toolkit).The original registration accuracy is 0.88?0.22mm,while it can be reduced to 0.70?0.11mm after optimization.And the model experiment shows that the uniform distribution of registration markers in dentistry can be realized and the overall registration accuracy can be improved.(2)The double calibration algorithm was developed.And it was applied in the system to calibrate a guider and realize its pose visualization in the software interface.So,based on the dynamic images shown in system screen,doctors are able to conduct interlocking nail placement.Then,it was integrated with the prototype of the interlocking nail implantation system.Meanwhile,a precision verification method based on the 3D Slicer platform was proposed.The femur model experiments show that the distance and angular deviations were 1.50?0.20mm and2.73?1.09~o respectively.And it shows that a simple and efficient method for the accurate implantation of distal interlocking nail has been developed.(3)This paper proposed a virtual bit calibration algorithm.According to different length and size values of intraoperative bits and initial calibration matrix of the standard bit,the corresponding calibration matrices can be computed and outputted automatically.And its calibration accuracy is 1.36?0.18mm.Consequently,the difficulty of repeated calibration operations of handpieces can be solved.Using the optical navigation system as the control group for the skull model experiment,12implants were conducted in 3 skull models.The model experiment shows that the mean entry,end and angular deviation values were 1.41?0.18mm,1.81?0.16mm and 1.83?0.20~o respectively.6 implants were conducted in the maxilla of a pig,and the corresponding errors are 1.25?0.07mm,1.77?0.12mm and 1.73?0.26~orespectively.Based on the above algorithms,many open source software and platforms(VTK 8.2.0,IGSTK 5.2 and Qt 5.9,etc.)and Microsoft Visual Studio 2019,this paper developed the surgery navigation systems based on electromagnetic tracking(Tian Xuan Magnetic Distal Targeting System and Tian Shu Electromagnetic Surgery Navigation System in dentistry).And the corresponding accuracy verification methods were provided and conducted.As a result,the precise placement of interlocking nails and implant in dentistry can be realized.In a word,this study can improve the practicability of current surgical navigation systems and make EM navigation systems more popular in orthopedics and dentistry.