Standalone RF Self-Interference Cancellation System for In-Vivo Simultaneous Transmit and Receive (STAR) MRI

Area of Science:

• Magnetic Resonance Imaging (MRI)
• Radio Frequency (RF) Engineering
• Signal Processing

Background:

• Simultaneous transmit and receive (STAR) operation in MRI is challenging due to strong RF signal leakage between transmit and receive coils.
• Existing methods often require external synchronization signals or complex setups, limiting practical application.

Purpose of the Study:

• To develop and demonstrate a standalone RF self-interference canceller for 1.5T STAR MRI.
• To achieve high isolation between transmitter and receiver without external MRI console signals for initial calibration.

Main Methods:

• A standalone system utilizes a voltage-controlled oscillator (VCO) to generate a cancellation signal, manipulated by voltage-controlled attenuators and phase shifters.
• A field-programmable gate array (FPGA) with an analog-to-digital converter (ADC) calibrates the cancellation signal by analyzing the received signal.
• A wireless user board with an ESP32 microcontroller allows for fine-tuning of the system post-calibration.

Main Results:

• Achieved 74.2 dB of isolation between the transmitter and receiver.
• Calibration time was 94 seconds.
• Enabled in-vivo MR imaging with approximately 40 mW of RF peak power.

Conclusions:

• The standalone STAR system effectively cancels RF self-interference, enabling high-isolation STAR MRI.
• The system's independence from external synchronization signals simplifies calibration and enhances practicality.
• Demonstrated feasibility of in-vivo STAR MRI with significantly reduced RF power.