Research On Spine Surgery Training System Based On Force Feedback And Immersion Virtual Reality Technology

Objectives:To establish a highly realistic spine surgery virtual surgery environment.The constitutive equation of the operation force and the parameter is constructed,and the process of spinal surgery is simulated by tissue deformation simulation.Analyze the impact of the system on the user's actual surgical skills.Part 1 The construction of virtual operation environmentMethods:1.Subject:The study of the body specimens from the Second Military Medical University Department of anatomy,a total of 10,including 5 males,the average age is 60 years old,height 172 cm,weight 73 kg;female 5,the average age is 55 years old,162 cm tall,weighing 53 kg.2.The specimens were taken,scanned by the 256-slice spiral CT,and then transferred to our project team computer system.3.Use the DICOM viewer to read the CT data,convert it to JPEG format,and convert the image to BMP format with ACDSee9.0 software.4.Image segmentation and 3D reconstruction were performed with Mimics10.0 to generate a 3D visualization spine model.5.The spine model is geometrically modeled by the marching cube algorithm.After the model is reconstructed,the material is edited by 3dMax software to realize the texture rendering of the model.6.The tool is measured by the vernier caliper,and the tool parameters are obtained.Then,the virtual operation tool is 3D modeled by CAD software,and then the material is edited and mapped with different degree.7.The spine 3D reconstruction model and the simulation tool model were introduced into the FreeForm Modeling System,respectively,to establish the spinal surgery virtual surgery environment.Results:1.The spine specimens were successfully fabricated and the 964-layer images were obtained by a 256-slice spiral CT scan,a total of 507MB of data.2.Most of the BMP format data we get is very satisfied.There are a small number of sub-poor results is not good,we adjust the threshold by the late adjustment,then the results are satisfactory.3.The reconstructed spine bone model can be enlarged and reduced in three dimensions.Can be any angle of rotation,measurement,all-round observation of the anatomy of the spine.4.The three-dimensional model of the spine surgery tool is built in a realistic form,and various manipulations can be done by manipulating the manipulator.5.In the establishment of the virtual environment,the spine bone model and surgical tools have a strong three-dimensional,realistic form.Can be free to manipulate virtual surgery tools to achieve the target site in the spine related virtual operation.Conclusions:The image processing software Mimics10.0 can modify the CT data from the input-to-output multi-link.By setting the parameters of the 3D reconstruction can control the quality of the reconstruction model,get accurate and smooth 3D model of the spine.In the establishment of the virtual environment,the spine bone model and surgical tools have a strong three-dimensional,realistic form.The operator can manipulate the virtual surgery tool to simulate the actual surgical procedure.This virtual environment has a strong sense of reality,immersion,interactive.Part2 Construction of Spinal Surgery Training System Based on Force Feedback TechniqueMethods:1.The analysis of surgical operation force data and force model creation(1).The project is designed by CNC machine tools,KISTLER precision dynamometer and data acquisition card,data acquisition and analysis software,signal amplifier.(2)We use KISTLER precision dynamometer and data acquisition card data acquisition and analysis software to measure the real operation force and torque during drilling operation.(3)We analyzed the collected data after denoising and analyzed the statistical analysis to establish multiple regression prediction model.We first analyze the influencing factors(independent variables)and manipulated forces(dependent variables)to determine the correlation between the dependent variables and the independent variables,and finally determine the correlation coefficients in the forecasting model.Constructing the constitutive equation of the operation force and the influence parameter.After the data was denoised,the regression was predicted and the regression analysis was carried out.(4)We first determine the relationship between the operating force and the various parameters.Then the constitutive equation of the input parameter and the output feedback force is established.And finally get the basis of the calculation of real operation.2.Collision detection and deformation simulation(1)According to the morphological characteristics of the tool,the tool model is discretized as a multi-point target,and the spatial relationship between the bone tissue voxel model and the tool point set is detected in real time.At the same time,the target point set of spatial interference with the bone tissue voxel model is recorded.(2)The operation force generated by each target point where the interference has occurred is calculated by calculating the position transformation vector between the current position and the previous position by combining the operation force constitutive equation.According to the spatial vector coordinates of each target point,the total operating force is calculated and feedback in real time.(3).The bone tissue voxels that interfere with the target set of targets are removed based on the fixed direction convex hull bounding box level,and the tissue deformation is simulated.3.The realization of the spine surgery virtual training system(1)Integrate the data interfaces of virtual systems(from the first part),deformation simulation and force feedback simulations(derived from the previous section),and other major systems.The key algorithms are implemented by modular software.(2)Based on VC2008 development platform,we use OpenGL as the graphic image library,and use Qt cross platform development library to complete the interactive interface design,and through the DLL dynamic link library and COM component technology to encapsulate the functional software system seamless integration.(3)Use the Swiss ForceDimension Omega7 as a force feedback device.Results:1.The drilling force measurement platform we created can measure the surgical operation force of the pedicle screw implantation on the fresh vertebral specimen by the dynamometer and the data acquisition system of the experimental platform and can record it in real time.The data can be analyzed and processed by the special data analysis software in the experimental platform.2.The drilling force and torque increase as the feed rate increases,but decreases as the spindle speed and drill diameter increase.3.We obtained the regression analysis of the obtained data:F = 77.42 ×d1.294Di0.317Vs-0.472Vf0.424(N)(1)M = 0.056 × d0.539Di2.371Vs0.106Vf0.024(N·m)(2)The preliminary drilling force prediction model is as follows:F = 6.45 +0.31Vfeed-4.7Vrot +7.8Vfeed2 +5.2Vrot2-6.1Vfeed·VrotIn the formula,F is the axial drilling force,Vfeed is the feed speed of the drill,and Vrot is the drill speed of the drill.4.We avoid the problem of discontinuity and distortion of the force feedback calculation when the bone density is not uniform by the multi-point collision detection algorithm,which improves the authenticity and stability of the feedback force calculation in the deformation simulation.5.The research group developed a set of spinal surgery virtual surgery training system with force feedback function.The system's force feedback device can be realistic force from the operator's hand to the arm,can accurately measure the three-dimensional space in the palm of the movement and rotation.Virtual bone tissue can produce a realistic effect without external steps.Through the 3D glasses operators can experience immersive virtual visual effects,to achieve visual and tactile interaction simulation.Conclusions:We obtained the regression equation of the obtained data and obtained the constitutive equation between the operation force and the parameter:F = 6.45 + 0.31Vfeed-4.7Vrot+7.8Vfeed2+5.2Vrot2-6.1Vfeed·VrotMulti-point Collision Detection Algorithm for Continuous Force Calculation of Force Feedback.The virtual surgery training system through the force feedback device,can be realistic force from the operator's hand to the arm,realistic simulation of the use of surgical tools for bone tissue operation when the bone tissue deformation.Through the 3D glasses operators can experience immersive virtual visual effects,to achieve visual and tactile interaction simulation.Part3 The Performance Evaluation of the Virtual Surgery Assisted SystemMethods:1.By recording the operating parameters and virtual feedback force of the virtual drilling operation in the system,it is compared with the real operation data under the same conditions.And then verify the credibility of the system.2.Through a detailed and comprehensive questionnaire to test whether the system has reached its intended purpose of the design.3.Through the control group comparison operation test.The physical model operation data of the two groups of trainees before and after the virtual training are recorded and compared,and the differences between them are compared,so the structural validity of the system is evaluated.4.Set quantitative evaluation indicators.The virtual training system was used to train the trainees repeatedly,and the data of the operation after the operator was trained on the actual model was analyzed.Then the virtual operation system was tested to achieve the expected training effect,so as to evaluate the conversion validity of the system.Results:1.The actual measurement data and the theoretical value are not exactly the same,but the actual measurement results fluctuate up and down in the theoretical value,showing a normal distribution.Therefore,we can think that our virtual surgery training system of the spindle force and torque simulation results have a high degree of reliability.2.In the three evaluation indicators given,medical school graduate students and senior doctors have given a "good" evaluation,indicating that the training system has a high surface validity.But in the system in the simulation details there is room for improvement,the novice has a better training effect.3.After repeated training by the system can improve the skills of doctors at different levels,and the system can ensure that experienced doctors get better performance.4.After repeated training operators can improve their practical skills and surgical proficiency,surgical training can be effectively converted into surgical experience.The system has a high conversion efficiency.Conclusions:The spine surgery virtual surgery training system constructed by this research group can accurately simulate the tactile touch of the drill operation in the actual operation,and simulate the "feel" in the actual operation.This training system is visually realistic,and the tactile feedback is stable and can be lifelike to restore the site of the surgery.The operator can effectively transform the surgical training effect into the surgical experience through the training of the system.Can distinguish between different levels of users.The system has high reliability,surface validity,result validity and conversion validity.But there are room for improvement in the details of the simulation,the novice has a better training effect.