External RF Mixer for Platform-Independent Motion Sensing with Beat Pilot Tone

Motivation: The original Beat Pilot Tone scheme offers the ability to choose arbitrary frequencies beyond the Larmor frequency for increased motion sensitivity. However, it relies on the nonlinearity of the scanner preamp, limiting its adaptability. Goal(s): Design an external mixing device that removes BPT's reliance on preamp nonlinearity. Approach: BPT was performed with and without the device on a coil with poor BPT reception. The presence of BPT signals and any effect on image SNR following device addition was evaluated. Results: Adding the device yielded stronger BPT signals without significantly impacting noise levels. Impact: Our hardware augmentation removes dependence on platform-specific nonlinearities by externalizing the BPT intermodulation process to a well-characterized device. This allows BPT, a novel and effective motion detection scheme, to be widely applied across scanner platforms.