To develop a new optically controlled on-coil amplifier that facilitates safe use of multi-channel RF transmission in MRI by real-time monitoring of signal phase and amplitude.
Monitoring was performed 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 7T MRI experiments.
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 1 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.