Research On A Prostate Robot And Its Needle Insertion Motion Planning In MR Environment

With the development of clinical application of imaging technology and medical robots, the combination of MR image and prostate robot for the diagnosis and treatment of prostate diseases will become a development trend.However, limited operation space in closed MR image scanner seriously restricts the development of prostate robot configuration. Furthermore, on prostate MR images, the boundary is fuzzy and the internal gray distribution is not uniform,which is difficult to provide a clear target point and the region location information for prostate robot. In addition, the narrow space of the perineum and needle deflection in tissue brings some difficulties to the motion planning of the prostate robot. In this paper, we study the prostate robot configuration, the segmentation method of prostate MR image and the motion planning of prostate robot based on MR image in MR environment.In view of the limited space in the MR scanner, the configuration of the prostate robot in MR environment is studied. According to the analysis of the MR scanner in the working space, patient position, prostate surgery space, the type of robot 2R3T degrees of freedom is got based on the spiral theory. Based on the constraint condition of the spiral theory and the actual constraints of the needle insertion operation, the configuration of the pair of five degrees of freedom (RZyYRYRZRY) robot configuration is obtained. According to the configuration of the robot, the main structure of the robot and the design of the needle insertion structure are designed. In order to meet the conditions of the robot’s closed solution, the robot wrist is designed by cross design. Through the static analysis and modal analysis of the main structure of the robot and the needle insertion mechanism, the rationality of the structural design of the robot is further verified. Based on the D-H coordinate transformation, the kinematics equation of the robot is established, and the analytical solution is obtained.According to the internal and external contours of all prostate segmentation problem, on the basis of the analysis of the anatomical structure and MR image signal, a prostate MRI two-step segmentation method is present using distance regularized level set evolution. And taking clinical regional division of central gland and peripheral zone with guiding significance as a priori knowledge and theoretical foundation of prostate segmentation method research, the effective whole segmentation of outer and inner contour of the prostate is finished. The human-machine interactive interface of the prostate segmentation is designed to study the image segmentation of ten prostate cases (including 30 images of normal, hyperplasia and cancerous prostates). Which verifies that the two-step MRI segmentation method of prostate based on the edge distance regularized level set evolution is effective to realize the whole segmentation of internal and external contour of a prostate.In order to solve the problem of how to reach the target of the whole prostate through little operating space of perinaeum and under the situations of needle deflection in tissue, the motion planning method of the prostate is studied.The system of the prostate robot is established, and the relationship between the major structure and needle insertion mechanism, between the robot and the MR image is established. Based on virtual nonlinear spring model, to build the needle deflection motion model in tissue, the parallel needle insertion based on virtual target, the point-fixed and tilted needle insertion based on virtual, and tilted needle insertion based on nested genetic algorithm are proposed. And the selection basis of different planning method is given.To verify accuracy of needle insertion motion planning method of prostate robot, a simulation system of the prostate robot is built based on Autodesk Inventor software and a human-machine interactive interface of the needle insertion motion planning of the robot is designed using Matlab software.Meanwhile, the simulation results of different motion planning method are valued. In order to realize the needle movement of the prostate target based on the MR image, the experiment platform of prostate needle insertion is established.On basis of testifying repeat positioning accuracy and stability of needle insertion motion at the same target point, the needle insertion into internal target point of prostate is studied. According to the real passing point information showed by each MRI to ajust the needle insertion path, which make the needle gradually approaching to the target points, resultly the needle insertion motion of inner target points is preferably realized. The experiment results are analysed.