基于肝脏力模型的机器人辅助进针策略

针对机器人辅助穿刺手术中软组织形变引起的安全性和准确性问题,基于猪肝进针力模型,在分析猪肝组织结构和力学特性的基础上提出了机器人辅助进针策略.它主要包括两点:一是在穿刺针进入肝脏瞬间,机器人自动停止进针,待软组织松弛片刎后,再以减半速度继续进针,以尽可能减小软组织形变对穿刺精度的影响,提高手术准确性.二是在穿刺针进入肝...     

Flexible needle posture control stratagem for ultrasound-based puncture manipulator system

This paper introduces a flexible puncture method that can improve the efficiency and safety of robot-assisted central venous catheterization (CVC) surgery systems. Current CVC surgery-assisted manipulators and systems are mainly focused methods for puncture needle insertion into blood vessels. There is no single systematic stratagem for safe high-precision control of the posture of the needle in a blood vessel after needle insertion. However, this type of control stratagem is both necessary and urgently required in surgery to avoid piercing the central vein and to provide a suitable posture for guide wire insertion. Therefore, we propose the remote centre of motion control method to control the needle’s posture precisely and safely. Verification experiments were performed in both a simulator and a puncture manipulator. The results indicate that the needle tip trajectory in the simulation is completely accurate and it also agrees well with the theoretical value. The positional and angular errors of the needle tip are smaller than 0.8?mm and 1.8°, respectively, in the real puncture manipulator experiment; these errors are sufficiently small for surgeries. The proposed design is practical and can be used in real puncture manipulators and systems.     

A new path planning method for bevel-tip flexible needle insertion in 3D space with multiple targets and obstacles

In this paper, a new bevel-tip flexible needle path planning method based on the bee-foraging learning particle swarm optimization (BFL-PSO) algorithm and the needle retraction strategy in 3D space is proposed to improve the puncture accuracy and shorten the puncture distance in the case of multiple puncture targets. First, the movement of the needle after penetrating the human body is analyzed, and the objective function which includes puncture path error, puncture path length, and collision function is established. Then, the BFL-PSO algorithm and the needle retraction strategy are analyzed. Finally, medical images of the tissue to be punctured are obtained by medical imaging instruments, i.e., magnetic resonance (MR), and the 3D model of the punctured environment is constructed by 3D Slicer to obtain the environment information on targets and obstacles, and the path of flexible needle is carried out based on the BFL-PSO optimization algorithm and the needle retraction strategy. The simulation results show that, compared with other path planning methods in the related literature, the new path planning method proposed in this paper has higher path planning accuracy, shorter puncture distance, and good adaptability to multi-target path planning problems.     

针穿刺软组织变形有限元仿真

为了提高机器人辅助针穿刺精度,提出一种对软组织变形分析的准静态有限元法.该方法基于针受力下软组织变形机理,将软组织变形的连续动态过程分解成离散的准静态过程;采用重叠单元法在ANSYS中建立了软组织变形的二维和三维准静态有限元模型,并进行了仿真实验.最后通过实验结果验证了该方法的有效性和可行性.     

Detection of needle puncture to blood vessel by using electric conductivity of blood for automatic blood sampling

Although blood sampling is frequently performed, a system to take blood sample automatically has not yet been developed. To achieve needle control for automatic blood sampling, the changes in puncture force and electric conduction by blood were evaluated. An injection needle with electric conduction electrode was set on a device for measuring puncture force by using a loadcell. When the needle punctured a blood vessel, blood flowed into the needle and caused a short circuit between electrodes attached on the skin surface and inside of the needle. Totally 18 of puncture experiments were carried out on vein of a rabbit's ear. The peak of puncture force caused by piercing the vessel wall and the electric conduction by the blood, were simultaneously observed in successful cases. When the needle pierced the vein out, no peak of puncture force but the electric conduction of the blood was obtained. This result shows that the electric conduction by blood can be applied to control needle insertion to the vein for automatic blood sampling.     

The Path-of-Probability Algorithm for Steering and Feedback Control of Flexible Needles

In this paper we develop a new framework for path planning of flexible needles with bevel tips. Based on a stochastic model of needle steering, the probability density function for the needle tip pose is approximated as a Gaussian. The means and covariances are estimated using an error propagation algorithm which has second order accuracy. Then we adapt the path-of-probability (POP) algorithm to path planning of flexible needles with bevel tips. We demonstrate how our planning algorithm can be used for feedback control of flexible needles. We also derive a closed-form solution for the port placement problem for finding good insertion locations for flexible needles in the case when there are no obstacles. Furthermore, we propose a new method using reference splines with the POP algorithm to solve the path planning problem for flexible needles in more general cases that include obstacles.     

Predicting part deformation based on deformation force data using Physics-informed Latent Variable Model

Part deformation prediction and control is a crucial issue for obtaining tight dimensional accuracy so as to ensure product quality with high performance, and deformation prediction is the fundamental of the deformation control. However, existing machining deformation prediction methods are based on the prediction or measurement of residual stress and suffering from two challenges: (i) the measurement accuracy of residual stress field is limited by physical principle and (ii) low prediction in accuracy. In order to address these issues, this paper presents a method for predicting part machining deformation based on deformation force using the proposed Physics-informed Latent Variable Model involved physics knowledge. Deformation force is introduced to represent the inner unbalanced residual stress state of the workpiece, and it is a much easier and more accurate signal compared with residual stress. Machining deformation is predicted by fusing the data-driven method and the prior knowledge of deformation mechanical relationship by taking advantage of the latent variable. The proposed method was verified both in simulation and actual machining environment, and accurate machining deformation prediction has been achieved. The proposed method can be readily extended to the prediction problems involved with difficult-to-measure physical quantities.     

一种结构解耦的新型应变式三维力传感器研究

维间耦合一直是制约多维力传感器精度提高的重要因素,结构解耦也一直是多维力传感器追求的目标。提出了一种新型三维力传感器,可用于Fx、Fz、My3个维度广义力的测量,其敏感原理是结构解耦的,因此可具有更高的精度。介绍了这种新型三维力传感器的结构并分析其敏感原理。采用有限单元法对应变式三维力传感器进行结构静力仿真,利用ANSYS后处理器提供的路径映射技术,精确地获得了应变片的贴片区域。仿真结果表明,该新型传感器与目前的应变式多维力传感器相比,维间耦合误差有明显改善,维间干扰由传统结构的3.56%降低至0.40%。     

基于图像形态学的软组织变形测量方法研究

为了准确测量针穿刺过程中的软组织变形,提出了一种基于图像形态学的软组织形 变测量方法。阐述了边缘检测、图像膨胀和腐蚀等算法,获取组织内标识物增强图像。提取标识 物重心位移,并存入测量矩阵M 中。搭建了包括精密运动装置、工业相机、光源和嵌入标识物的 水凝胶假体等组成的组织形变测量平台。实时采集了穿刺过程图像,并利用形态学算法测量了组 织内标识物的位移。经误差补偿后,组织形变测量误差小于0.7 mm。该方法可提高机器人辅助针 穿刺手术精度。     

Hand gesture guided robot-assisted surgery based on a direct augmented reality interface

Radiofrequency (RF) ablation is a good alternative to hepatic resection for treatment of liver tumors. However, accurate needle insertion requires precise hand-eye coordination and is also affected by the difficulty of RF needle navigation. This paper proposes a cooperative surgical robot system, guided by hand gestures and supported by an augmented reality (AR)-based surgical field, for robot-assisted percutaneous treatment. It establishes a robot-assisted natural AR guidance mechanism that incorporates the advantages of the following three aspects: AR visual guidance information, surgeon's experiences and accuracy of robotic surgery. A projector-based AR environment is directly overlaid on a patient to display preoperative and intraoperative information, while a mobile surgical robot system implements specified RF needle insertion plans. Natural hand gestures are used as an intuitive and robust method to interact with both the AR system and surgical robot. The proposed system was evaluated on a mannequin model. Experimental results demonstrated that hand gesture guidance was able to effectively guide the surgical robot, and the robot-assisted implementation was found to improve the accuracy of needle insertion. This human–robot cooperative mechanism is a promising approach for precise transcutaneous ablation therapy.     

基于虚拟弹簧模型的柔性针穿刺仿真研究

在分析柔性针受力和挠曲的基础上,建立二维空间上柔性针穿刺软组织的虚拟弹簧模型,得到针体和针尖轨迹的数学模型。使用Matlab工具软件对针尖轨迹在不同情况下进行仿真。仿真实验结果表明,柔性针弹性变形量对针尖走向影响较小,影响针尖走向的主要因素是纵向控制坐标和针座与水平线初始夹角,且两者的叠加效应最终影响柔性针走向,可以为机器人辅助针穿刺操控提供理论基础,结合软组织变形研究,能够实现柔性针穿刺的轨迹规划和避障运动。     

Interaction model between elastic objects for haptic feedback considering collisions of soft tissue

The simulation of organ–organ interaction is indispensable for practical and advanced medical VR simulator such as open surgery and indirect palpation. This paper describes a method to represent real-time interaction between elastic objects for accurate force feedback in medical VR simulation. The proposed model defines boundary deformation of colliding elements based on temporary surface forces calculated by temporary deformation. The model produces accurate deformation and force feedback considering collisions of objects as well as prevents unrealistic overlap of objects. A prototype simulator of rectal palpation is constructed on general desktop PC with a haptic device, PHANToM. The system allows users to feel different stiffness of a rear elastic object located behind another elastic object. The results of experiments confirmed the method expresses organ–organ interaction in real-time and produces realistic and perceivable force feedback.     

自适应SVD–UKF算法及在穿刺状态估计中的应用

柔性针在实际穿刺过程中会产生不规则形变, 导致柔性针模型存在参数不确定性问题, 影响穿刺精度. 本文针对柔性针穿刺过程存在的不确定性问题以及超声成像等设备存在的量测噪声统计特征不准确性问题, 提出了一种带有噪声估计器的自适应奇异值分解无迹卡尔曼滤波算法. 该算法采用自适应因子实时修正动力学模型误差, 通过奇异值分解抑制系统状态协方差矩阵的负定性, 利用Sage-Husa估计器在线估计噪声的统计特性, 减小了系统状态估计误差. 将新算法应用于带有曲率不定性的柔性针穿刺模型进行计算仿真, 仿真结果显示, 新的算法较现有的UKF算法相比, 估计误差减小了0.28 mm(82.7%), 与AUKF算法相比, 估计误差减小0.06 mm(52%). 因此, 新算法可有效改善滤波性能, 提高穿刺状态的估计精度.     

基于超声图像的PICC智能穿刺医疗机器人控制系统设计

为提高静脉穿刺置管手术的穿刺成功率,缓解病人所承担的生理性伤痛,设计基于超声图像的PICC（Peripheraly Inserted Central Cathcte,外周静脉置入的中心静脉导管）智能穿刺医疗机器人控制系统。以晶振复位电路作为穿刺置管的输出动力支持,通过驱动控制电机的传输调度作用,实现对智能传感器的精准化控制,降低置管过程中针头的平均进入深度,完成PICC智能穿刺医疗机器人及其控制应用结构搭建。在此基础上,按照静脉置管图像的实际特征分析结果,转换原有的超声图像格式,经过多次边缘性检测,实现对穿刺超声图像的初级预处理。获取静脉靶向血管的位置信息,在规划穿刺路径的同时,完成对机器人操作手的重定位控制,实现医疗机器人的运动控制模型分析。仿真对比实验结果显示,与常规静脉穿刺手段相比,穿刺控制系统可将进针角数值控制在10°-40°之间、进针深度保持在整个针头的2/3以内,可大幅提升穿刺置管的成功几率,实现减轻病人所承担生理性疼痛的目的。     

Simulating a syringe behavior using a pneumatic cylinder haptic interface

Mastering medical gestures, such as epidural needle insertion, requires much practice. Haptic interfaces can be efficient training solutions. Nevertheless, they must provide users with an accurate experience for an effective training. This article introduces a control framework that turns a pneumatic cylinder into a haptic interface able to simulate a syringe and more specifically the loss of resistance phenomenon encountered during an epidural needle insertion. To achieve this, the framework switches between two control laws (position and force tracking) according to the system state. Experiments involving two anesthetists confirm the practicality of this system for hands-on training or rehearsal purposes.     

Inelastic uniform torsion of steel members

This paper develops a mitre model for the shear strain distribution in steel members under uniform torsion. The mitre model provides reasonable approximations for the shear stress distributions, except near re-entrant corners, and accurate predictions of the fully plastic uniform torque. The elastic torque-twist relationship is predicted with high accuracy, and the inelastic relationship with reasonable accuracy. The mitre model uses a simple approximation to the shear strain distribution caused by uniform torsion. It can be expected to provide a relatively simple method of predicting the inelastic behaviour of steel members when uniform torsion acts in combination with axial force and bending moment.     

Needle Insertion Parameter Optimization for Brachytherapy

This paper presents a new needle path planning method for the insertion of rigid needles into deformable tissue. The needle insertion point, needle heading, and needle depth are optimized by minimizing the distance between a rigid needle and a number of targets in the tissue. The optimization method is based on iterative simulations performed using a tissue finite element model. At each iteration, the best 3-D line fitted to the displaced targets in the deformed tissue is used as a candidate for a new insertion line. First, this method is implemented in a prostate brachytherapy simulator under different boundary conditions to minimize the targeting error. It is shown that the optimization method converges in a few iterations and decreases the seed misplacement error to less than the needle diameter. Second, the efficacy of the optimization algorithm is verified by optimizing the insertion parameters for a brachytherapy needle before insertion into a prostate tissue phantom. The elastic properties of the phantom and the needle-tissue interaction parameters were identified in an independent experiment. The optimization algorithm is effective in decreasing the targeting error.     

基于LabVIEW的力觉检测系统

研究了手术过程中穿刺针与生物组织的相互作用力,对穿刺力进行了建模,搭建了生物软组织的力觉检测系统,检测系统由软、硬件2部分组成.其中,硬件平台采用了德国生产的高精度位移平台为穿刺针提供动力,利用压阻式力传感器进行力信号检测,并通过数据采集卡实时收集力信号.软件平台利用LabVIEW编程控制电机的运动和数据采集.利用平台进行了针穿刺实验,并利用MATLAB对实验数据进行了处理和分析,得出了穿刺力—位移曲线及其与影响因素的关系.     

Modelling and analysis of a novel CT-guided puncture robot for lung brachytherapy

In this paper, we present a novel CT-guided needle puncture robot system with seven degree of freedoms. All basic requirements of interventional radiology can be met. To solve the space constraints and compatibility requirement, tendon-sheath transmission is used as the drive mode of the end-effector. According to the kinematics analysis of the robot configuration, the reachable workspace is obtained, which can completely cover the chest of patient. Based on the Jacobian matrix, dimension parameters are optimised for better flexibility and kinematic performance in the workspace. Since respiratory movement will cause real-time motion of the tumour, a method is proposed to decrease the puncture error caused by respiratory movement. And the feasibility of this method is verified by puncture experiment based on independent design of respiratory motion simulation device. It is proved that this method will lead to an increase in the puncture accuracy by 2.4 times. In addition, the CT compatibility of the robot is verified, and the positioning accuracy is also measured through the experiments.     

基于环境特征和随机方法的柔性针路径规划

针对柔性针软组织穿刺路径规划问题,提出了一种基于环境特征和随机方法的规划算法。该方法采用单轮车模型,运用快速搜索随机树算法得到样本路径,再基于路径长度、弧段数、安全度及障碍物风险分级相结合的路径评估函数,得到最优路径。在路径生成过程中,医生可根据临床经验设置评估函数的权重系数及判断障碍物的风险等级,以适用不同组织的穿刺环境。进行复杂环境下柔性针软组织穿刺路径规划仿真,结果表明该方法环境适用性强,算法交互性好,具有较好的应用潜力。