An optically coupled system for quantitative monitoring of MRI-induced RF currents into long conductors.
An optically coupled system for quantitative monitoring of MRI-induced RF currents into long conductors.
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一种光学耦合系统，用于定量监测 MRI 感应进入长导体的射频电流。
DOI：
10.1109/tmi.2009.2031558
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发表时间：
2010
影响因子：
10.6
通讯作者：
Scott,GreigC
中科院分区：
文献类型：
--
作者：
Zanchi,MartaG;Venook,Ross;Pauly,JohnM;Scott,GreigC
磁共振成像（MRI）中的射频（RF）场在导丝等长导体中感应出的电流是导致周围介质（如组织）发热的潜在危险因素。本文提出了一种光耦合系统，有可能定量测量这些导体上感应的射频电流。该系统采用自屏蔽环形换能器和有源电路来调制高速发光二极管发射器。塑料光纤将光引导到光电二极管接收器和跨导放大器。系统确认包括一系列使用裸导丝的实验，这些实验比较了荧光温度计的导丝头端加热与射频电流传感器响应。在定制的全身64 MHz鸟笼测试平台和1.5 T MRI扫描仪上进行确认。利用该系统，可以模拟出电缆陷阱电流衰减、介质损耗、Q破坏甚至横波波节斑等现象。该系统应可应用于起搏器电极导线和导丝等介入器械的MRI射频安全性研究。特别是，该器械的变体可能在MRI引导介入期间充当实时安全监测器。
The currents induced in long conductors such as guidewires by the radio-frequency (RF) field in magnetic resonance imaging (MRI) are responsible for potentially dangerous heating of surrounding media, such as tissue. This paper presents an optically coupled system with the potential to quantitatively measure the RF currents induced on these conductors. The system uses a self shielded toroid transducer and active circuitry to modulate a high speed light-emitting-diode transmitter. Plastic fiber guides the light to a photodiode receiver and transimpedance amplifier. System validation included a series of experiments with bare wires that compared wire tip heating by fluoroptic thermometers with the RF current sensor response. Validations were performed on a custom whole body 64 MHz birdcage test platform and on a 1.5 T MRI scanner. With this system, a variety of phenomena were demonstrated including cable trap current attenuation, lossy dielectricQ-spoiling and even transverse electromagnetic wave node patterns. This system should find applications in studies of MRI RF safety for interventional devices such as pacemaker leads, and guidewires. In particular, variations of this device could potentially act as a realtime safety monitor during MRI guided interventions.
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