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Research On Puncture Path Planning Of Breast Intervention Robot Under MRI Environment

Posted on:2016-01-02Degree:DoctorType:Dissertation
Country:ChinaCandidate:H Y DuFull Text:PDF
GTID:1108330470970419Subject:Mechanical Manufacturing and Automation
Abstract/Summary:PDF Full Text Request
Magnetic resonance imaging(MRI) offers a new means of guidance for image-guided breast interventional surgery because of its excellent image quality. However, the compatibility problem of the high magnetic field of MRI environment and the limitation of the narrow workspace in MRI scanner hinder the application of the breast intervention robot in MRI environment. On the other hand, during the surgery, the interaction between needle bevel tip and soft tissue will cause the needle deflection and the needle tip will deviate from predetermined direction, so the needle tip deflection and path optimization are also the urgent problems. A breast intervention robot compatible with MRI environment is presented in this thesis. Needle deflection during the needle insertion into soft-tissue is modeled using principle of minimum potential energy. And then the puncture path planning for the robot is stuided based on the needle deflection model(NDM).Aiming at the characteristics of the breast interventional surgery, such as the high magnetic field, limited workspace and the prone position of a patient, the compatibility of the breast intervention robot under MRI environment is studied and an optimal structure is designed. Through the MRI scanning, experiments of compatibility test for different materials are made, and the image quality analysis based on Boolean subtraction operation are performed using Matlab software, which provides a scheme for the compatibility problem. The contradiction matrix in TRIZ theory is used to provide an innovative solution for the robot structure. An improved Cartesian-coordinate robot is proposed by using “functional analysis” and “inventive principle” and “substance-field model” and the optimization structure for the breast intervention robot under MRI environment is obtained. A remote driving means for robot based on flexible axles is proposed.Analysis of the needle-tissue interaction force is made. Discretization method is used that the friction on per unit of the needle shaft is regarded to be constant as on a stiffness straight needle shaft, and then the friction model of the whole needle shaft is set up by using integration method. The three-dimensional distribution characteristics of the cutting force acted on needle tip is analyzed, based on which, the cutting force is modeled by means of the needle-tissue interaction stiffness of per unit length. The cutting force can be resolved from the puncture force based on the quasi-static equilibrium equation, so that the parameters of the cutting force model are obtained.Taking account of the nonlinear and anisotropism of the soft tissue, the needle-tissue interaction model is established during the process of breast intervention by using virtual nonlinear springs. The needle is regarded as a cantilever beam supported by a series of nonlinear springs with different stiffness. Based on virtual nonlinear spring model and cutting force model mentioned above, the needle deflection is calculated by using the principle of minimum potential energy and Rayleigh-ritz method, and then the trajectory of the needle tip during insertion is obtained.Aiming at the requirements of avoiding primary laticifers and blood vessel in the breast during intervention process, based on the analysis of the robot kinematics, the path form of needle insertion is analyzed, and a path optimization method is proposed based on the NDM. An objective function for the path optimization is set up to optimize the insertion point and pose, regarding the insertion length and the safty of the needle insertion. The path optimization and simulation programs are written by Matlab software, and the simulation results show that the proposed method can obtain an optimal path under a complex three-dimensional environment.The tissue phantom is prepared using agaropectin, and a robot-controlled experimental system for target puncturing is established. The experimental results showed that, in the needle deflection experiment, the maximum absolute error of needle tip trajectory was less than 0.4mm and the average absolute error was less than 0.2mm; in the path optimation testing experiment,the maximum error of target puncture was less than 1.2mm and the average error was less than 0.9mm. All the experimental errors were within 2mm, which meets the requirement of the interventional surgery. The experimental results proved the accuracy of the NDM based on the virtual nonlinear springs and the effectiveness of the path optimization algorithm based on the NDM.
Keywords/Search Tags:magnetic resonance imaging(MRI), breast intervention robot, needle-tissue interaction model, path planning
PDF Full Text Request
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