柔性针穿刺软组织变形机理及动态轨迹规划方法研究

发布时间：2018-01-18 12:07

本文关键词：柔性针穿刺软组织变形机理及动态轨迹规划方法研究　出处：《浙江大学》2017年博士论文　论文类型：学位论文

【摘要】：穿刺针是应用在一般活检、局部麻醉、介入放射和近距治疗等外科诊疗中最基本的微创手术器械。大量外科诊断、治疗和研究都需要针穿刺到特定靶点,其中大多数穿刺靶点都集中在软组织器官。靶点位置运动和针穿刺运动轨迹的不确定性而引起的穿刺靶点误差严重限制了针刺手术的临床应用。本论文以柔性针精确穿刺动态靶点为目标,深入分析了柔性针与软组织之间交互作用机理,提出了基于改进局部约束法的软组织变形有限元模型,采用MATLAB程序包实现了穿刺过程组织变形的二维仿真,实验验证了所提算法的有效性。将计算机实验分析方法应用于软组织内部靶点和障碍物运动的实时预测,建立了基于Kriging元模型的组织变形预测模型,与有限元计算结果对比表明Kriging预测模型能够克服有限元计算代价大的缺陷。利用机器人运动学理论建立了穿刺过程中柔性针运动学模型,描述了针座与针尖之间的运动传递关系,进而建立了以调整角为控制参数的针体逆运动学方程,实验结果验证了运动学模型的正确性。利用人工势场概念定义了考虑靶点和障碍物运动的广义穿刺误差,利用针体正逆运动学方程将组织变形动态环境下的轨迹规划问题转化为广义穿刺误差优化问题,并提出了具体轨迹规划算法,实验验证了动态轨迹规划算法的可行性。本论文共分六章,主要内容简述如下:第一章,详细介绍了计算机辅助软组织针穿刺技术的研究背景和现状,归纳出针穿刺误差原因分类及表现。综述了柔性针穿刺软组织过程中针与软组织相互作用机理、柔性针操控技术及穿刺运动规划等方面的研究现状,分析了现有组织变形模型和轨迹规划方法存在的挑战。最后概述了本论文的主要研究内容和目标。第二章,在线弹性软组织有限元模型和柔性针悬臂梁模型的基础上,基于改进局部约束法建立了柔性针-软组织耦合模型,将针节点上作用力关系融入到软组织模型中。采用MATLAB软件实现了针穿刺软组织过程仿真。设计了与仿真条件相同的实验环境,并通过在PVA假体内部添加标识物来记录节点位移情况,分析和比较了靠近针约束、远离针约束和靠近边界约束等三类节点位移的实验和仿真结果,平均误差在0.50mm以内。所提耦合算法可拓展适用于非线性非匀质软组织材料。第三章,将计算机实验分析和元模型方法应用于软组织内部靶点和障碍物运动的实时预测。介绍了Kriging元模型的基本原理和计算机实验设计的拉丁超方格方法。建立了考虑软组织和针材料性能参数、穿刺角度等11个变量的软组织最大位移Kriging预测模型,分析了不同相关函数的预测性能和参数敏感性。建立了基于泛函响应的软组织变形实时预测Kriging模型,分析了模型对参数变化和时间指标变化的适应性能;与有限元仿真结果对比表明,Kriging实时模型预测相对残差在35%之内,可较好地反映组织变形规律。第四章,在分析柔性针挠曲作用机理的基础上,利用机器人运动学理论建立了斜角柔性穿刺针的正向和逆向运动学模型。采用准静态思想,对挠曲针体分段研究,将穿刺过程分解为n个子过程,每个子过程针尖运动可分解为两个旋转运动和一个平移运动,利用D-H方法描述了针座与针尖之间的运动关系。搭建了运动学实验平台,实验结果表明运动学模型预测与实验针尖偏移量误差在0.80mm之内,靶点穿刺误差小于0.78mm,能够符合柔性针在软组织内部的变形规律。第五章,在讨论针体逆运动学解存在性的基础上,提出了无障碍和有障碍静态环境下的针体轨迹规划方法。利用欧式距离和人工势场概念定义了考虑避障和中靶的广义穿刺误差,将动态环境下轨迹规划问题转化为穿刺误差优化问题,结合Kriging软组织实时模型提出了动态轨迹规划算法。实验结果表明,所提出的静动态轨迹算法综合考虑了针体的操控性能和轨迹可行性,均可获得可行的柔性针穿刺轨迹。第六章,归纳总结了本论文的主要研究工作,并对柔性针穿刺软组织的后续研究工作进行了展望。
[Abstract]:The puncture needle is used in biopsy, local anesthesia, minimally invasive surgical instruments and the most basic radiation therapy and surgery intervention. A large number of surgical diagnosis, treatment and research are needed to target specific needle, most puncture target points are concentrated in soft tissue. Clinical application of puncture point error target moving point target the position and needle trajectory uncertainty caused by severely limiting the acupuncture operation. In this paper, the flexible needle puncture accurate dynamic target as the goal, in-depth analysis of the mechanism of interaction between the flexible needle and soft tissue, a finite element model of soft tissue deformation method based on improved local constraints, using MATLAB program the package to achieve a two-dimensional simulation procedure of deformation, experiments verify the effectiveness of the proposed algorithm. The computer experiment analysis method is applied to the soft tissue inside the target and obstacles. Real time dynamic prediction, prediction model is established for deformation of Kriging element model based organization, and finite element calculation results show that the prediction model can overcome the defects of Kriging finite element computational cost. The robot kinematics is established based on the theory of flexible needle puncture process kinematics model, describes the relationship between the needle tip and transfer movement, and then set up to adjust the angle of the needle body control parameters of the inverse kinematics equation, the experimental results verify the correctness of the kinematic model. Considering the generalized puncture target and obstacle motion error was defined by the artificial potential field concept, using the needle body kinematics equation will organize deformation trajectory planning problem in dynamic environment is transformed into a generalized puncture error optimization problems, and puts forward the specific trajectory planning algorithm, the experiments verify the feasibility of dynamic trajectory planning algorithm. This paper is divided into six chapters, The main contents are as follows: the first chapter introduces the research background and present situation of computer aided soft tissue needle technique, summarizes the classification and performance of needle puncture error causes. The paper reviews the mechanism of flexible needle puncture needle in the process of soft tissue and soft tissue interaction, research status of flexible needleoperation technology and motion planning and other aspects of the puncture and the analysis of the existing tissue deformation model and the method of trajectory planning challenges. Finally summarizes the main contents of this paper and the target. In the second chapter, based on line elastic finite element model of soft tissue and flexible needle cantilever beam model, the flexible needle - soft tissue coupling model is established based on the method of improving local constraints, integrate the needle node force in relation to the soft tissue in the model. The simulation of needle insertion into soft tissue by MATLAB software. The design and Simulation of the same experimental environment and conditions. To record the node displacement by adding markers in PVA internal analysis and comparison of the prosthesis, near the needle constraint, the experimental and simulation results from needle constraint and near the boundary constraints of three types of node displacement, the average error is less than 0.50mm. The proposed method can be applied to a coupling nonlinear inhomogeneous soft tissue material third. Chapter, real-time prediction method and experimental analysis of element model of computer application in target and obstacle motion inside the soft tissue. The Kriging element model and basic principle of computer experimental design method. The establishment of the Latin square test and needle material properties of soft tissue parameters into account, the maximum displacement of Kriging soft tissue puncture angle of 11 a variable prediction model, sensitivity analysis of prediction performance and parameters of different correlation functions are established. The real-time prediction of Kriging model of soft tissue deformation based on the analysis of the functional response, mode The change of parameters and time indicators of adaptive performance; compared with the results of finite element simulation, real-time Kriging prediction model for relative error within 35%, can reflect the deformation rule of organization. In the fourth chapter, based on the analysis of flexible needle deflection mechanism, the robot kinematics is established based on the theory of forward and inverse kinematics model of angle the flexible puncture needle. The quasi static thought, research on the deflection of the needle body segment, the puncture process is divided into n sub processes, each sub process of tip motion can be divided into two rotating motion and a translational motion, using the D-H method to describe the motion relationship between the seat and the needle tip. Build the kinematics experimental platform, experimental the results show that the kinematics model prediction and experimental tip offset error within 0.80mm, target puncture error is less than 0.78mm, can meet the flexible needle in soft tissue inside Deformation law. The fifth chapter discussed the inverse kinematics of the needle body solutions on the basis of the proposed accessibility and needle trajectory planning method for obstacle in static environment. Use the Euclidean distance and the artificial potential field is defined considering the generalized error avoidance and puncture target, the trajectory planning problem in dynamic environment into the puncture error optimization problem, combined with the Kriging soft tissue model is proposed for the dynamic real-time trajectory planning algorithm. The experimental results show that the static and dynamic trajectory algorithm proposed considering the control performance and the feasibility of the trajectory of the needle body, can obtain the flexible needle trajectory feasible. The sixth chapter summarizes the main research work of this thesis, and follow-up study of flexible needle insertion into soft tissue are discussed.

【学位授予单位】：浙江大学
【学位级别】：博士
【学位授予年份】：2017
【分类号】：R446.8

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