Offline impedance measurements for detection and mitigation of dangerous implant interactions: an RF safety prescreen.
Offline impedance measurements for detection and mitigation of dangerous implant interactions: an RF safety prescreen.
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DOI：
10.1002/mrm.25202
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发表时间：
2015-03
影响因子：
3.3
通讯作者：
Scott, Greig C.
中科院分区：
文献类型：
--
作者：
Ellenor, Christopher W.;Stang, Pascal P.;Etezadi-Amoli, Maryam;Pauly, John M.;Scott, Greig C.
关键词：
研究了“射频安全预筛选”的概念，即通过射频线圈中的阻抗变化来检测MRI中使用的射频场与患者体内的导电植入物之间的危险相互作用。回顾了耦合振荡器的行为，并讨论了由此产生的可观察到的阻抗变化。鸟笼线圈装载有静态头部体模和导线体模，其中导线接近其谐振长度，其形状、位置和方向可以改变。使用电流传感器和网络分析仪来探测相互作用。在强耦合的情况下，阻抗谱显示出明显的分裂，并且在感应电流和散射参数之间有很强的相关性。一种新的低功率预筛选技术的可行性已经在一个简单的体模实验中得到证明，它可以明确地检测植入的导线和成像线圈之间的共振相互作用。还提出了一种可以检测导线的并行传输零模的新技术。Magn Reson Med 73：1328-1339,2015。©2014 Wiley期刊，Inc.
The concept of a “radiofrequency safety prescreen” is investigated, wherein dangerous interactions between radiofrequency fields used in MRI, and conductive implants in patients are detected through impedance changes in the radiofrequency coil. The behavior of coupled oscillators is reviewed, and the resulting, observable impedance changes are discussed. A birdcage coil is loaded with a static head phantom and a wire phantom with a wire close to its resonant length, the shape, position, and orientation of which can be changed. Interactions are probed with a current sensor and network analyzer. Impedance spectra show dramatic, unmistakable splitting in cases of strong coupling, and strong correlation is observed between induced current and scattering parameters. The feasibility of a new, low-power prescreening technique has been demonstrated in a simple phantom experiment, which can unambiguously detect resonant interactions between an implanted wire and an imaging coil. A new technique has also been presented which can detect parallel transmit null modes for the wire. Magn Reson Med 73:1328–1339, 2015. © 2014 Wiley Periodicals, Inc.
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