High power and high isolation transmit/receive switch for ultra-high field whole-body magnetic resonance imaging

The radio frequency (RF) transmit/receive (T/R) switch with high isolation in magnetic resonance imaging (MRI) systems plays a crucial role in managing the flow of RF signals between the transmitter and the receiver. For ultra-high field (UHF) MRI systems, the impact of parasitic parameters in high-power devices becomes increasingly significant, leading to the frequency shift of the traditional T/R switch using 50 Ohms λ/4 transmission lines, which in turn leads to a deterioration in isolation at the target frequency. This will increase the risk of receiving circuit damage in the transmit mode and RF interference in the receive mode, thereby degrading image signal-to-noise ratio (SNR) and resulting in image artifacts. In this study, a T/R switch with a novel resonant circuit was proposed for 5 T whole-body MRI under high-frequency and high-power conditions. As a result, the novel T/R switch with a high power capability of 8 kW can provide a high isolation of 38.8 dB in the transmit mode and an isolation of 46.2 dB in the receive mode, while the traditional T/R switch provided an isolation of 19.0 dB in the transmit mode and an isolation of 23.6 dB in the receive mode at the target frequency. Most importantly, the novel T/R switch can reduce image artifacts and insertion loss. As a result, higher SNR with an improvement of 15.7% has been achieved using the novel T/R switches. These results demonstrate that the proposed T/R switch can be applied in UHF whole-body MRI with reliability and safety in high-power transmission.