Radiology, Massachusetts General Hospital, Charlestown, Massachusetts.
Harvard Medical School, Boston, Massachusetts.
Magn Reson Med. 2020 Jan;83(1):299-311. doi: 10.1002/mrm.27905. Epub 2019 Aug 7.
To assess the mean and variance performance of parallel transmission (pTx) coils for reduction of the absorbed power around electrodes (APAE) in patients implanted with deep brain stimulation (DBS) devices.
We simulated 4 pTx coils (8 and 16 channels, head and body coils) and a birdcage body coil. We characterized the RF safety risk using the APAE, which is the integral of the deposited power (in Watts) in a small cylindrical volume of brain tissue surrounding the electrode tips. We assessed the APAE mean and variance by simulation of 5 realistic DBS patient models that include the full DBS implant length, extracranial loops, and implanted pulse generator.
PTx coils with 8 (16) channels were able to reduce the APAE by >18× (>169×) compared to the birdcage coil in average for all patient models, at no cost in term of flip angle uniformity or global specific absorption rate (SAR). Moreover, local pTx coils performed significantly better than body arrays.
PTx is a possible solution to the problem of RF heating of DBS patients when performing MRI, but the large interpatient variability of the APAE indicates that patient-specific safety monitoring may be needed.
评估平行传输（pTx）线圈在降低深部脑刺激（DBS）植入患者电极周围吸收功率（APAE）方面的均值和方差性能。
我们模拟了 4 个 pTx 线圈（8 通道和 16 通道、头线圈和体线圈）和一个鸟笼体线圈。我们使用 APAE 来描述射频安全风险，APAE 是电极尖端周围脑组织小圆柱体内沉积功率（瓦特）的积分。我们通过模拟 5 个具有完整 DBS 植入长度、颅外回路和植入脉冲发生器的现实 DBS 患者模型来评估 APAE 的均值和方差。
与鸟笼线圈相比，所有患者模型的平均 APAE 均降低了 >18×（>169×），8 通道（16 通道）的 pTx 线圈在不影响翻转角均匀性或全局比吸收率（SAR）的情况下实现了这一目标。此外，局部 pTx 线圈的性能明显优于体数组。
pTx 是解决 MRI 期间 DBS 患者射频加热问题的一种可能方法，但 APAE 的个体间差异很大，表明可能需要进行针对患者的安全性监测。
