肝脏肿瘤热消融术是一种微创、安全的经皮介入手术，已经成为根治肝癌的重要手段之一。由于手术操作的复杂性，肝脏肿瘤热消融术对医生的经验和技能有较强的依赖性。穿刺手术机器人在穿刺任务中表现出良好的稳定性和精准性，越来越多的应用于临床穿刺手术，但目前应用场景大多针对神经外科、骨科等刚性靶区，对于肝肿瘤热消融等胸腹部靶区，由于会受到呼吸运动影响，靶点位置不固定，限制了穿刺手术机器人在肝肿瘤热消融中的应用。本文针对自由呼吸下穿刺这一应用场景开展研究，旨在拓展穿刺手术机器人在肝肿瘤消融中的应用。本文主要工作如下：（1）搭建了一套超声引导的穿刺手术机器人系统。区别于通用的商业化手术导航系统，本系统主要针对自由呼吸运动下肝脏肿瘤热消融术等经皮介入手术。针对穿刺手术场景，系统提供了协作穿刺和自动穿刺两种工作模式。协作穿刺模式下医生能够通过系统控制机械臂，从而完成穿刺操作，自动穿刺模式下系统将对靶点实时位置进行监测，并结合术前规划路径生成穿刺决策，控制机械臂完成自主穿刺。（2）改进系统标定算法。其一，改进了针尖标定算法。基于机械臂自动控制原理，提出了一种自动针尖标定方法，解决了消融针等软性材质器械的标定难题，提升了针尖标定的自动化水平以及精度。其二，优化了原有手眼标定算法，将自动针尖标定方法应用于手眼标定，提出自动针尖-手眼标定算法，与传统手动针尖-手眼标定方法对比，标定精度提升了约57.7%。（3）提出了二维超声引导下机械臂穿刺姿态调整算法。首先定义了机械臂穿刺姿态的三大约束条件：针体处于穿刺平面，针轴与术前规划的穿刺路径共线以及固定于针的跟踪器始终朝向光学定位系统，根据约束条件构建方程，计算了满足穿刺约束条件的机械臂位姿，进而控制机械臂完成姿态调整。（4）提供了一套自由呼吸运动下进行穿刺的解决方案，利用FRE值反映呼吸运动与术前规划时呼吸状态的差异，FRE值较小时进行穿刺，反之等待下一穿刺间隙。同时搭建了一套呼吸运动仿真实验平台用于可行性及精度验证，在周期性呼吸运动下，对运动靶点的穿刺误差小于2.00mm。本文研究结果初步证明，呼吸运动下穿刺手术机器人有着应用潜力，一方面能够为医生提供精准导航，另一方面能够补偿呼吸运动带来的靶点位移。
Liver tumor thermal ablation is a minimally invasive and safe percutaneous interventional surgery that has become one of the important means for the radical treatment of liver cancer. Due to the complexity of the operation, liver tumor thermal ablation relies heavily on the experience and skills of the surgeon. Puncture surgery robots have shown good stability and precision in puncture tasks and are increasingly used in clinical puncture surgeries. However, the current application scenarios are mostly for rigid target areas such as neurosurgery and orthopedics. For thoracoabdominal target areas like liver tumor thermal ablation, the target location is not fixed due to respiratory motion, limiting the application of puncture surgery robots in liver tumor thermal ablation. This paper conducts research on the application scenario of puncture under free breathing, aiming to expand the application of puncture surgery robots in liver tumor ablation. The main work of this paper is as follows:(1)A set of ultrasound-guided puncture surgery robot systems was built. Unlike general commercial surgical navigation systems, this system is mainly for percutaneous interventional surgeries such as liver tumor thermal ablation under free breathing. For puncture surgery scenarios, the system provides two working modes: collaborative puncture and automatic puncture. In collaborative puncture mode, doctors can control the robotic arm through the system to complete the puncture operation, while in automatic puncture mode, the system will monitor the real-time position of the target point, generate puncture decisions based on preoperative planning paths, and control the robotic arm to complete autonomous puncture.(2)The system calibration algorithm was improved. Firstly, the needle tip calibration algorithm was improved. Based on the principle of automatic control of the robotic arm, an automatic needle tip calibration method was proposed, solving the calibration problem of soft material instruments such as ablation needles and enhancing the automation level and accuracy of needle tip calibration. Secondly, the original hand-eye calibration algorithm was optimized, applying the automatic needle tip calibration method to hand-eye calibration, proposing an automatic needle tip-hand-eye calibration algorithm. Compared with the traditional manual needle tip-hand-eye calibration method, the calibration accuracy has improved by about 57.7%.(3)A two-dimensional ultrasound-guided robotic arm puncture posture adjustment algorithm was proposed. First, the three major constraints of the robotic arm puncture posture were defined: the needle body is in the puncture plane, the needle axis is collinear with the preoperative planning puncture path, and the tracker fixed to the needle always faces the optical positioning system. Based on the constraints, equations were constructed, the robotic arm‘s posture satisfying the puncture constraints was calculated, and then the robotic arm was controlled to complete posture adjustment.(4)A set of solutions for puncture under free breathing motion was provided, using the FRE value to reflect the difference between respiratory motion and the respiratory state at the time of preoperative planning. Puncture is performed when the FRE value is low, otherwise, wait for the next puncture interval. At the same time, a respiratory motion simulation experimental platform was established for feasibility and accuracy verification. Under periodic respiratory motion, the puncture error of the moving target was less than 2.00mm.The research results of this paper preliminarily prove that puncture surgery robots under respiratory motion have application potential, providing precise navigation for doctors on the one hand, and compensating for target displacement caused by respiratory motion on the other.
