Radio Frequency (RF) coils transmit and receive RF signals in magnetic resonance imaging (MRI). Designing FR coils is a challenge because they often have to operate at multiple frequencies and it is difficult to enable them to resonate at multiple frequencies or switch their resonating frequencies. Positive-intrinsic-negative (PIN) diodes are commonly used as electronic switches for switching the resonating frequencies in RF coils, however, their use often degrades the signal-to-noise ratio (SNR) due to high insertion loss and interference from additional biasing circuit components, which is critical for SNR-prioritized applications.
Researchers at Arizona State University have developed a novel control mechanism for adjusting and optimizing RF conditions using pneumatically-driven components, which include a switch (AeroSwitch), a capacitor (AeroCap) and a coil (AeroCoil). This system (AeroMR) addresses the challenges of electrical control of RF coils in MRI and MRS. The primary component, AeroSwitch serves as an RF switch alternative to PIN diodes by reducing lossy elements and additional biasing circuitry. In bench testing against the PIN diode systems, a slightly reduced average insertion loss of 0.1 dB and an enhancement in average isolation by 15 dB was observed as well as an average improved Q-factor of 62%.
The AeroMR system offers a promising advantage for MRI and MRS, where tunable RF coils are essential and maximizing SNR is critical.
Potential Applications
- Pneumatically-controlled RF coils
- MRI
- Spectroscopy
- Other medical related RF applications
Benefits and Advantages
- AeroSwitch offers significant advantages over the PIN diode due to its lower loss and higher isolation, potentially improving SNR
- The temperature of the AeroSwitch, while operating at 100 watts, remained consistently below 30°C, suggesting its potential as a self-temperature-regulated high-power switch
- AeroSwitch is non-magnetic, has high-power capability, low insertion loss, requires no electric biasing, and uses no conductive wires,
- This switching technique is significantly beneficial for MRI applications and other medical related RF applications
- Eliminates electronic control to achieve noise reduction
- Less susceptible to electromagnetic interference and thermal variations
- Integration and operation can be programmed or adjusted in real-time during MRI/MRS procedures
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