八通道并行发射-接收系统，用于 7T MRI，采用光控和监测的线圈内电流模式射频放大器。
Eight-channel parallel transmit-receive system for 7 T MRI with optically controlled and monitored on-coil current-mode RF amplifiers.
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. 2020 Dec;84(6):3494-3501. doi: 10.1002/mrm.28392. Epub 2020 Jul 14.
PURPOSE
To demonstrate a practical implementation of an eight-channel parallel-transmit system for brain imaging at 7 T based on on-coil amplifier technology.
METHODS
An eight-channel parallel transmit-receive system was built with optimized on-coil switch-mode current RF power amplifiers. The amplifiers were optically controlled from an eight-channel interface that was connected to a 7 T MRI scanner. The interface also optically received a down-converted version of the coil current sensed in each amplifier for monitoring and feedback adjustments.
RESULTS
Each on-coil amplifier delivered more than 100 W peak power and provided enough amplifier decoupling (<-15 dB) for the implemented eight-channel array configuration. Phantom and human images were acquired to demonstrate practical operation of this new technology in a 7 T MRI scanner.
CONCLUSION
Further development and improvement of previously demonstrated on-coil technology led to successful implementation of an eight-channel parallel-transmit system able to deliver strong B fields for typical brain imaging applications. This is an important step forward toward implementation of on-coil RF amplification for high-field MRI.
目的
展示基于线圈放大器技术的 7T 脑成像八通道并行发射系统的实际应用。
方法
构建了一个八通道并行发射/接收系统，采用优化的基于线圈的开关模式电流 RF 功率放大器。放大器通过连接到 7T MRI 扫描仪的八通道接口进行光控。该接口还对每个放大器中感应的线圈电流进行光接收，用于监测和反馈调整。
结果
每个线圈放大器都能提供超过 100W 的峰值功率，并为所实现的八通道阵列配置提供足够的放大器解耦（< -15dB）。采集了幻影和人体图像，以证明这项新技术在 7T MRI 扫描仪中的实际运行情况。
结论
进一步开发和改进之前展示的线圈技术，成功实现了一个能够为典型脑成像应用提供强 B 场的八通道并行发射系统。这是朝着实现高场 MRI 线圈 RF 放大迈出的重要一步。
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