Shooshtary S, Solbach K
Annu Int Conf IEEE Eng Med Biol Soc. 2015 Aug;2015:1572-5. doi: 10.1109/EMBC.2015.7318673.
A 7 Tesla Magnetic Resonance Imaging (MRI) system with parallel transmission (pTx) for 32 near-magnet Cartesian feedback loop power amplifiers (PA) with output power of 1kW is under construction at Erwin L. Hahn Institute for Magnetic Resonance Imaging. Variation of load impedance due to mutual coupling of neighborhood coils in the array may lead to instability of the Cartesian feedback loop amplifier. MRI safety requires unconditional stability of the PAs at any load. In order to avoid instability in the pTx system, conditions and limits of stability have to be investigated for every possible excitation mode for the coil array. In this work, an efficient method of stability check for an array of two transmit channels (Tx) with Cartesian feedback loop amplifier and a selective excitation mode for the coil array is proposed which allows extension of stability investigations to a large pTx array with any arbitrary excitation mode for the coil array.
埃尔温·L·哈恩磁共振成像研究所正在建造一台7特斯拉磁共振成像（MRI）系统，该系统具有并行传输（pTx）功能，用于32个近磁体笛卡尔反馈回路功率放大器（PA），输出功率为1kW。阵列中相邻线圈的相互耦合导致负载阻抗变化，可能会导致笛卡尔反馈回路放大器不稳定。MRI安全要求功率放大器在任何负载下都具有无条件稳定性。为了避免pTx系统中的不稳定性，必须针对线圈阵列的每种可能激励模式研究稳定性的条件和限制。在这项工作中，提出了一种针对具有笛卡尔反馈回路放大器的两个发射通道（Tx）阵列的高效稳定性检查方法，以及一种用于线圈阵列的选择性激励模式，该方法允许将稳定性研究扩展到具有任意激励模式的大型pTx阵列。
