基于悬臂梁模型的针挠曲预测

目的 分析针穿刺组织过程中的挠曲量和穿刺针受力情况,提高针穿刺精度。方法 搭建包括工业相机、步进电机和光源等组成的测量设备。用针轴直径分别为1.3、0.9、0.6 mm的穿刺针进行针穿刺软组织实验,利用力传感器得到不同穿刺速度（5、10和15 mm/s）下的穿刺力,通过数字图像处理得到穿刺针的挠曲量。在分析针受力的基础上,构建预测针挠曲量的悬臂梁模型。结果 利用悬臂梁模型对直径为1.3、0.6 mm穿刺针在5 mm/s速度下的挠曲量进行预测,其绝对误差小于0.5 mm,相对误差小于10%。结论 所建模型能够实现对针穿刺挠曲的预测,可以为机器人辅助柔性针穿刺路径规划和避障运动提供参考。     

基于悬臂梁模型的针挠曲预测

目的分析针穿刺组织过程中的挠曲量和穿刺针受力情况,提高针穿刺精度。方法搭建包括工业相机、步进电机和光源等组成的测量设备。用针轴直径分别为1.3、0.9、0.6 mm的穿刺针进行针穿刺软组织实验,利用力传感器得到不同穿刺速度(5、10和15 mm/s)下的穿刺力,通过数字图像处理得到穿刺针的挠曲量。在分析针受力的基础上,构建预测针挠曲量的悬臂梁模型。结果利用悬臂梁模型对直径为1.3、0.6 mm穿刺针在5 mm/s速度下的挠曲量进行预测,其绝对误差小于0.5 mm,相对误差小于10%。结论所建模型能够实现对针穿刺挠曲的预测,可以为机器人辅助柔性针穿刺路径规划和避障运动提供参考。     

基于悬臂梁模型的针挠曲预测

目的 分析针穿刺组织过程中的挠曲量和穿刺针受力情况，提高针穿刺精度。方法 搭建包括工业相机、步进电机和光源等组成的测量设备。用针轴直径分别为1.3、0.9、0.6 mm的穿刺针进行针穿刺软组织实验，利用力传感器得到不同穿刺速度（5、10和15 mm/s）下的穿刺力，通过数字图像处理得到穿刺针的挠曲量。在分析针受力的基础上，构建预测针挠曲量的悬臂梁模型。结果 利用悬臂梁模型对直径为1.3、0.6 mm穿刺针在5 mm/s速度下的挠曲量进行预测，其绝对误差小于0.5 mm，相对误差小于10%。结论 所建模型能够实现对针穿刺挠曲的预测，可以为机器人辅助柔性针穿刺路径规划和避障运动提供参考。     

三维超声影像导航机器人系统的临床应用

为了提高三维超声引导下微波消融治疗肝癌穿刺机器人系统的末端精度,本研究用指数积方法建立了穿刺机器人正运动学模型,设计了特殊神经网络标定方法,并对机器人末端位置进行了标定.标定实验结果表明,经过此种方法标定后的穿刺机器人,在手术常用工作空间内的末端位置精度提高100%以上.此系统已在北京301医院获得成功的临床实验应用,手术结果表明该系统可以准确定位病灶区域,精确放置手术器械,摆脱穿刺引导架的角度限制.介入治疗机器人实现了大角度准确穿刺并满足介入手术的需求,有效地提高了囊肿穿刺手术的治疗效果.     

手术针穿刺软组织建模技术研究现状

软组织穿刺在临床医学中有着越来越多的应用需求,但穿刺过程中手术针与组织的相互作用和生物组织复杂性往往会导致穿刺误差产生。本文主要从穿刺力和穿刺误差两个方面介绍了国内外手术针穿刺软组织建模技术研究现状。所有研究都表明,轴向力可以分解为多种不同类型力,如刚性力、摩擦力和切割力。穿刺的误差主要由针体挠曲和组织变形两个因素引起。当前的学者们提出了各种不同的数学和有限元模型,对穿刺过程进行了分析,以求对穿刺力和误差进行预测,优化穿刺针设计和穿刺策略,从而提高穿刺的准确率。本文还对依照当前模型提出的一些穿刺策略进行简述,从而为软组织穿刺的研究和应用提供参考。     

男性泌尿生殖系统数字化模型在解剖教学中的应用

数字化人体研究是将成千上万条人体断面数据信息在计算机里整合重建成人体的三维立体结构图像,构成人体形态学信息研究的实验平台[1]。建立三维数字化模型,不仅给解剖教学开辟了一个新的领域,而且为医学、影像诊断学、生命科学以及后基因组学的研究和应用提供基础数据与相应技术支撑。1男性泌尿生殖系统数字化模型的研究情况1.1基于3D-DOCTOR软件的三维重建将CVH-1可视化男性人体数据集的腹盆腔连续断面图像导入3D-DOCTOR软件,用该软件自带的分割工具逐层对泌尿生殖系统器官及部分重要毗邻结构进行数据分割,并行多边形面绘制三维重建…     

辐照仿真人体模型三维建模及装配原理与方法

辐照仿真人体模型是放射治疗和空间辐照研究的重要装备,实现其数字化建模,提高制造精度和仿真程度是仿真假人研究的重点和难点之一。以"成都剂量体模"(CDP)的序列CT切片集为源数据,运用MATLAB软件,通过图像预处理、图像提取等数字图像处理技术获得人体器官的点云数据;在CATIA软件Digitized Shape Editor模块中处理点云数据得到肝脏、肺、肾和胃等主要器官和组织的三维实体模型;以人体骨骼为基础建立人体器官装配坐标系;根据器官的"局部坐标系原点"、"标志点"和"特征点"与人体骨骼的相对位置,确定器官在人体器官装配坐标系中的坐标;利用Pro/E软件完成人体主要器官(异形体零件)装配。实验证明利用该方法建立的三维辐照仿真假人数字化模型与CDP具有较高的等效程度,为人体参数化设计奠定了理论基础,能够满足辐照仿真假人数字化生产的要求。     

用于肝癌介入治疗的术中三维超声导航系统

目前,介入治疗越来越多地被应用到肝癌患者的治疗中,相对于传统手术而言,介入治疗是一种简单、安全、有效的治疗方法。由于超声图像具有实时性,其被广泛地应用到介入治疗手术过程的导航。但是,在二维超声引导下,手术过程中病灶区域靶点的定位以及手术器械的精确放置难以达到实践的要求。本研究描述了用于肝癌介入治疗术中三维超声导航系统,该系统不仅可以提高穿刺路径规划,而且能够跟踪穿刺针并且实时的切片图像。通过试验证明,该系统穿刺精度可控制在5mm之内。该系统的应用可以准确定位病灶区域,精确放置手术器械,提高了手术的效果。     

XRII图像引导手术系统的研究与实现

本研究拟就实现XRII图像引导的手术系统之关键技术进行探讨。采用圆霍夫变换(CHT)与连通体(CC)分析结合法进行标志物识别与数据提取;采用移动最小二乘法(MLS)与层次B样条法(MBA)集成法进行XRII图像变形校正;采用Faugeras法进行C形臂成像系统标定。在此基础上,自行开发相关软件并结合手术工具设计制作,形成一整套实验型手术系统。人体脊柱标本实验表明,采用XRII图像引导的手术系统可明显提高椎弓根螺钉植入精度。     

微创肛瘘封堵器的结构设计与实验研究

目的 设计一种适用于肛瘘内口闭合手术的封堵器,研究封堵器的结构设计以及植入物与组织的相互作用,评估内口封堵性能。 方法 对封堵器进行整体结构设计与样机制作;建立封堵有限元模型,研究封堵过程中组织的应力分布及损伤面积;搭建组织穿刺实验平台对仿真模型及结果进行验证;搭建拔出力实验平台对内口封堵效果进行评估。 结果 封堵过程中,进给机构的最大扭矩为 36 mN·m,组织的最大应力为 19. 75 MPa,其损伤面积为1. 35 cm2。 有限元理论模型与实验结果基本吻合,最大拔出力达到 5. 11 N。 结论 封堵过程中的组织损伤面积满足肛瘘的微创治疗要求。 本文设计的微创肛瘘封堵器可实现内口的有效封堵,有助于医生更加便捷、快速、有效地完成肛瘘的微创手术。     

Vivo motion and force measurement of surgical needle intervention during prostate brachytherapy

In this paper, we present needle insertion forces and motion trajectories measured during actual brachytherapy needle insertion while implanting radioactive seeds in the prostate glands of 20 different patients. The needle motion was captured using ultrasound images and a 6 degree-of-freedom electromagnetic-based position sensor. Needle velocity was computed from the position information and the corresponding time stamps. From in vivo data we found the maximum needle insertion forces to be about 15.6 and 8.9 N for 17 gauge (1.47 mm) and 18 gauge (1.27 mm) needles, respectively. Part of this difference in insertion forces is due to the needle size difference (17G and 18G) and the other part is due to the difference in tissue properties that are specific to the individual patient. Some transverse forces were observed, which are attributed to several factors such as tissue heterogeneity, organ movement, human factors in surgery, and the interaction between the template and the needle. However, theses insertion forces are significantly responsible for needle deviation from the desired trajectory and target movement. Therefore, a proper selection of needle and modulated velocity (translational and rotational) may reduce the tissue deformation and target movement by reducing insertion forces and thereby improve the seed delivery accuracy. The knowledge gleaned from this study promises to be useful for not only designing mechanical/robotic systems but also developing a predictive deformation model of the prostate and real-time adaptive controlling of the needle.     

Use of puncture force measurement to investigate the conditions of blood vessel needle insertion

Central venous catheterization involves venous puncture and catheter insertion for transfusions. Quantitative conditions that facilitate insertion of the needle, such as the angle and velocity of insertion, have not been clarified. We previously developed a robotic system for guiding the needle along a specified puncture path with high precision and are currently implementing a hardware design for a robotic system to assist in blood vessel puncture. In this study, we proposed the insertion angle and velocity for stopping the needle in a blood vessel, assuming that a robotic system such as ours is used during the procedure. We inserted a needle into a segment of porcine jugular vein and obtained the puncture reaction force. Evaluation indices were the magnitude of the sudden decrease in reaction force at the point at which the needle advances and the length of time that the needle is present within the vein. Results indicated that the conditions under which it was easiest to stop the needle inside the vein were an insertion angle range of 10–20 and an insertion velocity of 3 mm/s.     

Measurement and Stochastic Modeling of Kidney Puncture Forces

The development of needle insertion robots and training simulators requires knowledge of the forces that arise when a needle is inserted into soft-tissue. The present study aims to construct stochastic models of the force required to puncture a kidney using a trocar needle, based on measurements. To this end, a total of sixty insertions were performed into porcine kidneys (ex vivo), at constant speed, using a linear motion stage. Axial force was measured at the needle hub and an ultrasound probe moved with the needle to enable identification of anatomical structures. Two force peaks were observed for each tissue layer punctured, one caused by the tip and one by the edge of the cannula. Based on ultrasound data these double-peaks were classified into four groups, related to kidney capsule and internal structures. Group size varied from 7 to 55 double-peaks. Force peaks in each group were evaluated in terms of peak force and drop in force for both tip and cannula, and stochastic models were constructed that describe the multivariate distribution of these metrics. Peak forces in the capsule and internal structures ranged up to 2 N and 8 N, respectively. The resulting models can be used to simulate kidney puncture events in a variety of applications.     

The importance of organ geometry and boundary constraints for planning of medical interventions

Realistic modeling of medical interventions involving tool-tissue interactions has been considered to be a key requirement in the development of high-fidelity simulators and planners. Organ geometry, soft-tissue constitutive laws, and boundary conditions imposed by the connective tissues surrounding the organ are some of the factors that govern the accuracy of medical intervention planning. In this study it is demonstrated that, for needle path planning, the organ geometry and boundary constraints surrounding the organ are the most important factors influencing the deformation. As an example, the procedure of needle insertion into the prostate (e.g. for biopsy or brachytherapy) is considered. Image segmentation is used to extract the anatomical details from magnetic resonance images, while object-oriented finite element analysis (OOF) software is used to generate finite element (FE) meshes from the segmented images. Two-dimensional FE simulations that account for complex anatomical details along with relative motion between the prostate and its surrounding structure using cohesive zone models are compared with traditional simulation models having simple organ geometry and boundary constraints. Nodal displacements for these simpler models were observed to be up to 14 times larger than those obtained from the anatomically accurate models.     

Detection of needle puncture to blood vessel using puncture force measurement

Although blood sampling is frequently performed, a system to take blood samples automatically has not yet been developed. In the paper, as a first step towards automatic blood sampling, an examination of an automatic method for puncturing blood vessels is described. The force waveforms produced by puncturing rabbit ear veins were measured. A characteristic peak, possibly associated with the needle piercing the vessel wall, was observed in each waveform of ten successful cases of 14 trials. An algorithm that allowed the detection of this peak was developed, and parameters of a filter to improve the accuracy of the algorithm were determined. Using this algorithm, automatic needle punctures were performed in a rabbit ear vein and then were simulated using the data derived from manual needle puncture on four other rabbits. The results gave 30 fully successful cases of 33 trials of needle puncture and showed that measurement of the puncture force may be important for automatic needle puncture of blood vessels.     

Needle insertion into soft tissue: a survey

Needle insertion in soft tissue has attracted considerable attention in recent years due to its application in minimally invasive percutaneous procedures such as biopsies and brachytherapy. This paper presents a survey of the current state of research on needle insertion in soft tissue. It examines the topic from several aspects, e.g. modeling needle insertion forces, modeling tissue deformation and needle deflection during insertion, robot-assisted needle insertion, and the effect of different trajectories on tissue deformation. All studies show that the axial force of a needle during insertion in soft tissue is the summation of different forces distributed along the needle shaft such as stiffness force, frictional force and cutting force. Some studies have modeled these forces. The force data in some procedures is used for identifying tissue layers as the needle is inserted or for path planning. Needle deflection and tissue deformation are major problems for accurate needle insertion and attempts have been made to model them. Using current models several insertion techniques have been developed which are briefly reviewed in this paper.     

Modeling and simulation of flexible needles

Needle insertion is performed in many clinical and therapeutic procedures. Tissue displacement and needle bending which result from needle–tissue interaction make accurate targeting difficult. For performing physicians to gain essential needle targeting skills, needle insertion simulators can be used for training. An accurate needle bending model is essential for such simulators. These bending models are also needed for needle path planning.In this paper, three different models are presented to simulate the deformations of a needle. The first two models use the finite element method and take the geometric nonlinearity into account. The third model is a series of rigid bars connected by angular springs. The models were compared to recorded deformations during experiments of applying lateral tip forces on a brachytherapy needle. The model parameters were identified and the simulation results were compared to the experimental data. The results show that the angular spring model, which is computationally the most efficient model, is also the most accurate in modeling the bending of the brachytherapy needle.