| As a breast cancer screening tool,nuclear magnetic resonance imaging(MRI)has strong sensitivity in tumor detection which can provide high precision image navigation for breast biopsy.However,the high magnetic field environment and very limited working space in MRI scanner restrict the application of breast biopsy robot in nuclear magnetic field.Developing an ideal transmission joint with small space,flexible transmission route,long distance power transmission and MRI-compatible is a difficult problem to be solved in the application of breast biopsy robot under nuclear magnetic field.In addition,due to the complexity of breast tissue composition,biopsy needle deflection occurs during puncture of multilayer tissue.Therefore,this paper designs a new type of remote breast biopsy accurate puncture robot system suitable for nuclear magnetic compatibility.In view of the stringent material requirements for the materials of the robot driver and transmission device in the MRI environment,on the basis of the analysis of the advantages and disadvantages of the existing MRI-compatible drive and transmission devices,a new remote bidirectional coupling double tendon-sheath modular transmission joint for MRI is designed.The coupling transmission joint of the double tendon-sheath can realize long-distance and large-stroke power transmission,which is suitable for placing the motor outside the scanner in MRI environment without special material driver.To solve the problem that the common drive wheel will be entangled in multi-layer winding,the LeBus thread groove is adopted in the bidirectional coupling drive wheel,and a friction model and transmission characteristic model of the double tendon-sheath bidirectional coupling transmission system with LeBus thread groove are established to improve the transmission accuracy.In view of the problem that the tension sensor can not be installed in the large-stroke transmission system,three-point force measurement is used to measure and set the preload of the new tendon-sheath transmission system.In addition,the correctness of the theoretical model is verified by transmission experiments and the transmission characteristics are explored through multiple sets of tests.Finally,the new tendon-sheath transmission system is compensated,and the experimental results meet the requirements of long-distance and large-stroke transmission accuracy of biopsy robot.Aiming at the problem of MRI strong magnetic field and limited operating space inside the scanner,based on the compatibility analysis of MRI-compatible breast biopsy robot,an MRI-compatible remote control breast biopsy robot system is designed.The system consists of a biopsy puncture module for breast biopsy in a limited space,a multi-angle fixed clamping tissue module for tissue fluidity,and an ergonomic support frame for patients with prolonged prone problem during biopsy in a limited space.The system allows the patient to be in the prone position to realize the doctor’s remote biopsy operation.By D-H method,the forward kinematics and inverse kinematics of the breast biopsy robot are analyzed,and the joint model workspace of the breast biopsy robot is analyzed by MATLAB/Simulink software and SolidWorks software,and then ANSYS/Workbench software is used to perform finite element analysis on the force of the prone support frame,robot clamping mechanism and transmission joint in the breast biopsy robot.The results show that the designed system can ensure the safe implementation of breast biopsy in the limited space of nuclear magnetic field.In view of the different characteristics of the patient’s breast tissue(fat,gland and tumor)lead to different needle entry path and deflection angle.Based on the analysis of the characteristics of breast tissue components,the geometric reconstruction method of MRI data for breast tumor patients in clamped and unclamped states is adopted,and a model of the curve puncture path of the breast biopsy robot to the multilayer tissue is proposed to solve the precise puncture problem of the breast biopsy robot under complex tissue composition.Aiming at the problem that the changes of needle state of needle tip in adipose tissue,gland tissue and tumor tissue during breast biopsy.In order to improve the accuracy of breast biopsy robot puncturing tumor tissue,a cantilever beam model of biopsy needle puncture multilayer tissue in quasi-static process is proposed to simulate the deflection of needle in multilayer tissue,and a biopsy robot’s model of multi-layer curve puncture path is established.Aiming at the remote control problem of breast biopsy robot based on double tendon-sheath transmission,the experimental platform is built,and the software system of upper computer is developed by using C++language through Qt software to realize the remote operation of breast biopsy robot.The motion control planning of breast biopsy robot is carried out according to the operation procedure of biopsy.In the light of the cantilever beam model of biopsy needle puncture multi-layer tissue,the experimental platform of biopsy needle and tissue puncture is built.The puncture force,friction force and deflection data of biopsy needle and two kinds of tissue are measured.The experimental results verified the correctness of the theoretical model.Finally,the experimental platform of breast biopsy robot based on double tendon-sheath transmission is built.According to the model of multi-layer tissue puncture path,the multi-layer tissue puncture experiment is carried out,and the results show that remote accurate breast biopsy surgery can be achieved. |
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