不同电导率介质下植入物射频致热表现的研究

Study on RF Heating of Implants in Different Conductivity Medium

在MRI检查中,植入物射频致热会对植入物佩戴者造成安全性影响。在人体中各组织电导率差异显著,而介质电导率又会对射频电场的分布造成影响,因此,需要对不同介质电导率的射频致热进行研究。该文从分析MRI射频致热的原理出发,构建了鸟笼线圈、ASTM标准体模和导线模型,并选取了数个人体中的典型组织电导率作为实验中的介质电导率。之后在64 MHz频率下计算导线的功率沉积。结果表明,介质电导率不会对电场和功率沉积的分布造成影响,不同电导率下热点分布不变;介质电导率越小,导线功率沉积越大,导线射频致热的温升越大;电导率与功率沉积的变化近似线性。而在2 W/kg全身特定吸收率的限值下,电导率减小,导线功率沉积急剧变大。

In MRI examination,RF heating of implants will affect the safety of implant wearers.The conductivity of various tissues in the human body is significantly different,and the medium conductivity will affect the distribution of the RF electric field.Therefore,it is necessary to study the RF heating of different medium conductivity.Based on the analysis of the principle of MRI RF heating,this study build the model of the bird cage coil,ASTM standard phantom and lead,and the conductivity of several typical human tissues is selected as the conductivity in the experiment.Then calculate the power deposition of the lead at 64 MHz.The results show that the medium conductivity has no effect on the distribution of electric field and power deposition,and the hot spot distribution remains unchanged under different conductivity;The smaller the conductivity is,the larger the power deposition of the lead is,and the greater the temperature rise of the lead caused by RF heating is;The change of conductivity and power deposition is approximately linear.At the limit of 2 W/kg whole body specific absorption rate(SAR),the conductivity decreases,and the wire power deposition increases sharply.