The Study Of 3-D Stereoscopic Display Mode Of The Navigation System For Endoscopic Sinus Surgery

Endoscopic sinus surgery (ESS) has been largely replaced the traditional open surgery, and become the main method of surgical treatment for sinonasal diseases. With the expansion of surgical scope and indication, as well as the wide application of endoscopic technique, serious complications, such as the damage of orbital and skull base, were increasing. Under the concept of precise surgery, endoscopic surgery navigation system aroused. Existing surgical navigation system can provided the relative position between surgical instrument and important anatomical structures to the surgeon accurately according to the preoperative imaging information, thus direct the surgeon to perform the operation safely and accurately. The commonly clinical used navigation system (electromagnetic or infrared) could met clinical demands in terms of tracking accuracy and convenience, however, they all adopted the "triplanar view mode" in the aspect of image display. Operator should reconstruction the location relationship between instrument and anatomical structures according to the coordinates of the instrument tip on sagittal, coronal and horizontal images and the real images obtained from nasal endoscope, so as to guide the surgery. To restore the position relationship between anatomical structures correctly, operators should depend on their subjective thinking and judgment based on anatomical knowledge and clinical experience to a large extent. Thus the building of the stereoscopic image will be different because of the difference on the understanding of the image data and familiarity with the anatomical structures. In addition, existing navigation system use the probe to verify the corresponding anatomical marks, this will frequently interrupt the operation and cause more time-consuming.Based on the above problems, on the basis of the hardware configuration of existing navigation system, we studied the stereo display mode based on augmented reality. The 3-D virtual image based on preoperative imaging data was designed as the background, and the real endoscopic image was matched and fused with it, so that the surgeon can observe the stereoscopic anatomic structure below the surface and the surrounding area. Thereby providing a more realistic and objective image to the operator, and reduce their dependence on subjective judgments. Eventually perform a more safe and effective operation.Part I:The study of calibration method for the coordinate on nasal endoscope in navigation system based on 3-D stereoscopic display mode.Objective:To study and raise the calibration method of endoscopic coordinates during the development of navigation system for endoscopic surgery based on augmented reality technique, to validate the calibration result by the mould experiment, and eventually form the unique positioning method of navigation system through the combination with navigation coordinate transformation matrix. Materials and Methods: To achieve the above goals, we utilized the calibration procedures provided by manufacturer of POLARIS Vicra infrared tracking system, the "endoscopy calibrator" developed by our team, and the innovative "conical pendulum method" to obtain calibration parameters of nasal endoscopy tips, and then redefined the coordinate of nasal endoscope. And to evaluate the calibration results of endoscopic coordinates by reference the offset error of the top coordinate of standard testing probe. Test the reliability of the method and the parameters obtained. Eventually substituted the accurate calibration parameter into coordinate transformation matrix, to lay a foundation for the future validation to the navigation accuracy. Results:we finally obtained the coordinates calibration parameters of endoscope by using the above methods. Comparing with standard reference, the statistical result showed no significant difference, substituted the calibration parameters into the navigation coordinate transformation matrix, the total transforming relation of the coordinates was deduced. Conclusion:During the process of the development of navigation system for nasal endoscopic surgery based on augmented reality technique, we achieved the accurate transformation of coordinate origin of nasal endoscope by "conical pendulum method". Verification results show that the method is feasible, the total coordinate transforming relation was obtained through substituting above parameters into navigation coordinate transformation matrix. It is notable that the navigation accuracy can be affected by many factors. The ultimate navigation effect should be validated in a series of further experiments.Part Ⅱ:The 3-D stereoscopic display mode navigation system for endoscopic sinus and skull base surgery:a feasibility study.Objective:To verify the reliability and clinical feasibility of a self-developed navigation system based on an augmented reality (AR) technique for endoscopic sinus and skull base surgery. Materials and Methods:In this study we performed a head phantom and cadaver experiment to determine the display effect and accuracy of our navigational system. We compared cadaver head-based simulated operations, target registration error, operation time, and National Aeronautics and Space Administration Task Load Index scores of our navigation system to conventional navigation systems. Results:The navigation system developed in this study has a novel display mode capable of fusing endoscopic images to three-dimensional (3-D) virtual images. The target registration error was 1.28 ± 0.45 mm, which met the accepted standards of a navigation system used for nasal endoscopic surgery. Compared with conventional navigation systems, the new system was more effective in terms of operation time and the mental workload of surgeons, which is especially important for less experienced surgeons. Conclusion:The self-developed augmented reality navigation system for endoscopic sinus and skull base surgery appears to have advantages that outweigh those of conventional navigation systems. We conclude that this navigational system will provide rhinologists with more intuitive and more detailed imaging information, thus reducing the judgment time and mental workload of surgeons when performing complex sinus and skull base surgeries. Ultimately, this new navigational system has potential to increase the quality of surgeries.Part Ⅲ:The preliminary application of the image-guided navigation system based on 3-D stereoscopic display mode for nasal endoscopic surgery in Sinuses, skull base and orbital surgeries.Objective To verify the accuracy of the image-guided navigation system based on augmented reality technique for nasal endoscopic surgery in clinical application, and to estimate the value of the system in sinus and skull base surgery. Method 2 cases of sinonasal neoplasm with skull base extension,3 cases of neoplasm with orbital extension and 7 cases of neoplasm confined in sinonasal cavity underwent the surgery using the self-developed navigation system. The accuracy and the surgical complication were recorded, the subjective aids supplied to operators were reflected by the results of Likert questionnaire and NASA-TLX visual analogue scale. In addition, we attempt to compare some key indicators with conventional surgery group, thus to preliminarily propose the advantage of the system. Result The average accuracy of the 12 cases of navigational surgery was 1.35±0.53mm. There were no operative complications in this group. The result of the Likert questionnaire and NASA-TLX visual analogue scale indicated that the subjective aid obtained from the navigation system were recognized. With the application of the system, the workload of the operator decreased and the confidence improved. Conclusion The accuracy of the new developed navigation system was proved to be reliable. The system has the potential to control the complication of the nasal endoscopic surgery, and to supply the subjective aid to the operator.