Objective

To propose and validate a variation of the classic techniques for the estimation of the transfer function (TF) of a real pacemaker (PM) lead.

Methods

The TF of three commercially available PM leads was measured by combining data from experimental measurements and numerical simulations generated by three sources: a) the experimental local SAR at the tip of the PM lead (single measurement point) exposed to a 64 MHz birdcage body coil; b) the experimental current distribution along the PM lead, obtained by directly injecting a 64 MHz signal inside the lead; c) the electric field (E-field) simulated with a computational model of the 64 MHz birdcage body coil adopted in the experimental measurement performed in a). The effect of the lead trajectory on the estimation of the TF was also estimated.

Results

The proposed methodology was validated by comparing the SAR obtained from the PM lead TF with experimental measurements: a maximum difference of 2.2 dB was observed. It was also shown that the estimation of the TF cannot be considered independent with the lead trajectory: a variation of the SAR estimation up to 3.4 dB was observed.

Conclusion

For the three PM lead tested, the error in the SAR estimation is within the uncertainty level of SAR measurements (± 2 dB). Additionally, the estimation of the TF using the reciprocity principle is influenced by the particular lead trajectory adopted, even if the consequent variability in the SAR estimation is still close to the uncertainty level of SAR measurements.

中文翻译：

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评估真实起搏器导线在 MR 射频感应加热中的传递函数的组合计算和实验方法

客观的

提出并验证用于估计真实起搏器 (PM) 导线传递函数 (TF) 的经典技术的变体。

方法

三个市售 PM 引线的 TF 是通过结合来自三个来源的实验测量和数值模拟的数据来测量的：a) 暴露于 64 MHz 鸟笼体线圈的 PM 引线尖端（单个测量点）的实验局部 SAR ; b) 沿 PM 引线的实验电流分布，通过直接在引线内部注入 64 MHz 信号获得；c) 在 a) 中进行的实验测量中采用的 64 MHz 鸟笼体线圈的计算模型模拟的电场（E 场）。还估计了前导轨迹对 TF 估计的影响。

结果

通过将从 PM 引线 TF 获得的 SAR 与实验测量值进行比较，验证了所提出的方法：观察到的最大差异为 2.2 dB。还表明不能将 TF 的估计视为独立于前导轨迹：观察到高达 3.4 dB 的 SAR 估计变化。

结论

对于测试的三个 PM 引线，SAR 估计中的误差在 SAR 测量的不确定性水平 (± 2 dB) 内。此外，使用互易原理对 TF 的估计受到所采用的特定前导轨迹的影响，即使 SAR 估计的后续可变性仍然接近 SAR 测量的不确定性水平。