带 RF 监测反馈的光控在线放大器。
Optically controlled on-coil amplifier with RF monitoring feedback.
机构信息
Laboratory of Functional and Molecular Imaging, National Institute of Neurological Disorders and Stroke, National Institutes of Health, Bethesda, Maryland, USA.
出版信息
Magn Reson Med. 2018 May;79(5):2833-2841. doi: 10.1002/mrm.26916. Epub 2017 Sep 14.
PURPOSE
To develop a new optically controlled on-coil amplifier that facilitates safe use of multi-channel radiofrequency (RF) transmission in MRI by real-time monitoring of signal phase and amplitude.
METHODS
Monitoring was carried out with a 4-channel prototype system by sensing, down sampling, digitizing, and optically transmitting the RF transmit signal to a remote PC to control the amplifiers. Performance was evaluated with benchtop and 7 T MRI experiments.
RESULTS
Monitored amplitude and phase were stable across repetitions and had standard deviations of 0.061 μT and 0.0073 rad, respectively. The feedback system allowed inter-channel phase and B amplitude to be adjusted within two iterations. MRI experiments demonstrated the feasibility of this approach to perform safe and accurate multi-channel RF transmission and monitoring at high field.
CONCLUSION
We demonstrated a 4-channel transceiver system based on optically controlled on-coil amplifiers with RF signal monitoring and feedback control. The approach allows the safe and precise control of RF transmission fields, required to achieve uniform excitation at high field. Magn Reson Med 79:2833-2841, 2018. © 2017 International Society for Magnetic Resonance in Medicine.
目的
开发一种新的光控在线放大器，通过实时监测信号相位和幅度，实现多通道射频（RF）传输的安全使用。
方法
通过感应、下采样、数字化，并将 RF 发射信号光传送到远程 PC 以控制放大器，使用 4 通道原型系统进行监测。通过台式和 7T MRI 实验对性能进行评估。
结果
在重复过程中，监测到的幅度和相位均保持稳定，其标准差分别为 0.061μT 和 0.0073rad。反馈系统允许在两个迭代内调整通道间相位和 B 幅度。MRI 实验证明了这种方法在高场下进行安全准确的多通道 RF 传输和监测的可行性。
结论
我们展示了一种基于光控在线放大器的 4 通道收发器系统，具有 RF 信号监测和反馈控制功能。该方法允许对 RF 传输场进行安全精确的控制，这是在高场实现均匀激发所必需的。磁共振医学 79:2833-2841,2018。©2017 年国际磁共振医学学会。
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