脑深部刺激微创电极的颅内植入运动机理及靶点定位误差控制研究

In order to solve problems such as inaccurate target location caused by the deformation or displacement of the tissue and motion error of the microelectrode with large ratio of the length to the diameter in deep brain stimulation surgery with minimally invasive. A novel target location error control method of microelectrode implanted, based on EEG signal features of the brain tissues during the DBS route, is presented by the intracranial dynamic modeling of the microelectrode, overfulfiling the difficult monitoring the microelectrode tip coordinate in order to reveal the microelectrode intracranial movement behavior and mechanism. To unify all the surgery error, breaking through the difficult caused by intracranial tissue deform and brain shift, the dynamic model of the microelectrode, interacted with the brain tissues, is built to simulating how the factors influence the motion error by coupled method of FEM and SPH methods. Moreover, the motion error factors regression mathematical model is built to analyze the error controlling strategies for optimal the structure parameters of the microelectrode. To research the optimal driving strategies of micro electrode, a reverse motion planning to get the parameters and method of optimal driving strategies is put forward based on the implant trajectory for avoiding important tissues and large blood vessels. For eliminating the detection difficult of the microelectrode intracranial position, A PID control model with feedback through intracranial movement position error of the microelectrode is proposed under monitoring position error during the implanted process from the EEG characteristic of each tissue, which is helpful to provide theoretical and technical guidance for DBS or other neurosurgeries.

为了解决脑深部刺激微创手术中因大长径比微电极弱刚度和颅内组织大变形及移位而导致的靶点定位不准等难题，从电极颅内动力学建模着手，创新性地提出基于各组织脑电信号特征的电极颅内运动误差控制方法，创建微电极颅内植入运动误差控制理论体系，全面揭示微电极颅内运动行为及误差产生机理。为归一术中误差，攻克颅内组织材料分层且大变形难点，采用仿真和试验相结合方式，利用FEM和SPH耦合方法，建立微电极颅内植入动力学模型。仿真并构建电极颅内植入运动误差影响因素的回归数学模型。基于避让血管和重要组织的植入理想路径，研究运动误差控制策略，逆向确定电极颅内植入的最优驱动方法和参数。为了突破电极颅内植入位置检测难点，提取各组织脑电信号的频率特征，结合各组织的影像坐标监控微电极植入过程的位置误差，建立微电极运动误差检测和PID控制模型，达到对微电极运动过程和靶点定位的精密控制，为DBS或其它神经外科手术提供理论和技术指导

针对丘脑底核脑深部刺激手术因穿刺理论缺乏、穿刺设备落后而导致的靶点定位精度低及颅脑损伤大的问题，本课题结合手术条件对穿刺涉及区域脑组织的材料力学属性进行了分区域研究。分析了大脑皮质刺破前套管电极对完整脑组织的小截面压缩作用及刺破后套管电极对穿刺路径上脑组织的径向压痕-松弛作用，建立了完整脑组织的穿刺力学模型及描述脑组织压痕-松弛过程的遗传积分模型。制备了完整猪脑组织样本，对其进行了穿刺测试；制备了含穿刺路径的大截面及大厚度脑组织切片，对穿刺路径通过的6个区域进行了压痕-松弛测试。求得了完整脑组织的弹性模量及穿刺路径上不同区域脑组织的剪切松弛模量，分析了不同区域脑组织材料力学属性的差异性。利用有限元仿真软件对电极植入脑组织的过程进行动态仿真，仿真结果表明：对直径为0.8mm的电极，其植入速度由1mm/s增加到4mm/s时，电极所受刺破力也随之增加，由0.09N增大到0.15N，加入电极旋转速度后电极的受力减少，电极的直径尺寸增加时电极尖端受力增加，由电极直线速度、旋转速度、电极直径对刺破力峰值的影响因素正交分析可知：电极直径对刺破力峰值的影响远远高于电极的直线速度和旋转速度对刺破力峰值的影响。对直径为0.2mm、0.3mm、0.4mm、0.5mm的微电极探针进行不同角度和不同长度的探针针尖偏移测量实验。实验结果表明长80mm的探针中，直径为0.5mm的探针在水平进针时探针针尖偏移量最小为0.238mm，在竖直进针时探针针尖偏移量为0。微电极植入策略方案。结合脑组织材料力学特性对微电极探针植入过程进行力学分析，提出旋转进给植入和往复进给植入的策略，通过力学模型揭示植入过程中力与速度的关系，力与偏移误差的关系。设计正交试验的方案，将直线植入、旋转植入、往复植入作为因素，直线速度、旋转速度、往复距离作为水平进行了九组实验。对实验数据进行直观分析和方差分析，得出对针尖误差影响的顺序从大到小分别是：旋转速度、往复距离和直线速度，并通过F对比对每个因素的影响程度进行了分析。