Modeling of electrodes and implantable pulse generator cases for the analysis of implant tip heating under MR imaging.
Modeling of electrodes and implantable pulse generator cases for the analysis of implant tip heating under MR imaging.
复制标题
电极和植入式脉冲发生器案例的建模，用于分析 MR 成像下植入物尖端的加热。
DOI：
10.1118/1.4921019
复制
发表时间：
2015
期刊：
影响因子：
3.8
通讯作者：
E. Atalar
中科院分区：
文献类型：
--
作者：
V. Acikel;A. Uslubas;E. Atalar
目的
作者的目的是使用集总电路元件对植入式脉冲发生器(IPG)和有源植入式医疗设备的电极进行建模，以分析它们在磁共振成像(MRI)检查期间对射频引起的组织加热问题的影响。
方法
在本研究中，IPG外壳和电极被建模为一个电压源和一个阻抗。利用改进的传输线方法(MoTLiM)和矩量法(MoM)模拟得到了这些参数的值。一旦确定了电极/IPG外壳模型的参数值，它们就可以连接到任何导线，并且可以分析针尖加热。为了验证这些模型，我们使用了MOM模拟和MR实验。利用所提出的模型和MoTLiM方法求解了具有IPG外壳或电极连接的引线上的感应电流。将这些结果与MOM模拟结果进行了比较。此外，电极通过电感连接到导线上。通过改变电感，用MoTLiM方法计算了电极上的耗散功率，并与用MoM法得到的比吸收率结果进行了比较。然后，对IPG病例和电极模型进行MRI实验验证。为了测试IPG表壳，将一根裸露的导线连接到表壳上，并将其放置在一个统一的模体中。在MRI扫描期间，通过改变导线长度来测量导线的温升。还使用IPG案例模型和MoTLiM计算了同一场景下的销售线索功率。然后，通过电感将电极连接到导线上，并将其放置在统一体模中。在MRI扫描期间，通过改变电感来测量电极上的温升，并与电极电阻上的耗散功率进行比较。
结果
采用MoTLiM和所提出的集总电路模型相结合的方法，求解了具有IPG外壳或电极连接的引线上的感应电流。将这些结果与MOM模拟的结果进行了比较。测定结果的均方误差小于9%。在MRI实验中，当引入IPG病例时，计算出的共振长度的误差小于13%。此外，还预测了端部温升在共振长度上的变化，误差小于4%。在电极实验中，对匹配阻抗的预测值误差小于1%。
结论
提出了IPG壳体和电极的电气模型，并给出了参数的确定方法。使用定义的电极阻抗和导线戴维南阻抗阐明了电极与导线匹配的概念。利用所提出的理论，可以预测IPG外壳和电极对尖端加热的影响。有了这些模型，理解植入物引起的组织加热变得更容易。此外，这些模型对种植体安全测试员和设计者也很有帮助。使用这些模型，可以确定最坏的情况，并可以计划相应的植入测试实验。
PURPOSE
The authors' purpose is to model the case of an implantable pulse generator (IPG) and the electrode of an active implantable medical device using lumped circuit elements in order to analyze their effect on radio frequency induced tissue heating problem during a magnetic resonance imaging (MRI) examination.
METHODS
In this study, IPG case and electrode are modeled with a voltage source and impedance. Values of these parameters are found using the modified transmission line method (MoTLiM) and the method of moments (MoM) simulations. Once the parameter values of an electrode/IPG case model are determined, they can be connected to any lead, and tip heating can be analyzed. To validate these models, both MoM simulations and MR experiments were used. The induced currents on the leads with the IPG case or electrode connections were solved using the proposed models and the MoTLiM. These results were compared with the MoM simulations. In addition, an electrode was connected to a lead via an inductor. The dissipated power on the electrode was calculated using the MoTLiM by changing the inductance and the results were compared with the specific absorption rate results that were obtained using MoM. Then, MRI experiments were conducted to test the IPG case and the electrode models. To test the IPG case, a bare lead was connected to the case and placed inside a uniform phantom. During a MRI scan, the temperature rise at the lead was measured by changing the lead length. The power at the lead tip for the same scenario was also calculated using the IPG case model and MoTLiM. Then, an electrode was connected to a lead via an inductor and placed inside a uniform phantom. During a MRI scan, the temperature rise at the electrode was measured by changing the inductance and compared with the dissipated power on the electrode resistance.
RESULTS
The induced currents on leads with the IPG case or electrode connection were solved for using the combination of the MoTLiM and the proposed lumped circuit models. These results were compared with those from the MoM simulations. The mean square error was less than 9%. During the MRI experiments, when the IPG case was introduced, the resonance lengths were calculated to have an error less than 13%. Also the change in tip temperature rise at resonance lengths was predicted with less than 4% error. For the electrode experiments, the value of the matching impedance was predicted with an error less than 1%.
CONCLUSIONS
Electrical models for the IPG case and electrode are suggested, and the method is proposed to determine the parameter values. The concept of matching of the electrode to the lead is clarified using the defined electrode impedance and the lead Thevenin impedance. The effect of the IPG case and electrode on tip heating can be predicted using the proposed theory. With these models, understanding the tissue heating due to the implants becomes easier. Also, these models are beneficial for implant safety testers and designers. Using these models, worst case conditions can be determined and the corresponding implant test experiments can be planned.
DOI：
10.1115/1.3127260
发表时间：
2009-07
期刊：
Journal of biomechanical engineering
影响因子：
--
作者：
Shrivastava D;Vaughan JT
通讯作者：
Vaughan JT
介入 MRI 中局部射频加热的格林函数方法。
影响因子：
3.8
作者：
Yeung,CJ;Atalar,E
通讯作者：
Atalar,E