Mimicking Transcranial Focused Ultrasound with a DC Loop Coil for Repeatable and Safe Development of Acoustic Radiation Force Imaging Methods

Motivation: New MR Acoustic Radiation Force Imaging (MR-ARFI) methods are needed to target ultrasound neuromodulation, but development is limited by the lack of robust acoustic coupling and current FDA ultrasound exposure limits. Goal(s): A repeatable and safe method to generate MR-ARFI signals in vivo without ultrasound. Approach: A DC loop coil was built that generates a pulsed magnetic field during MR-ARFI sequences, to mimic the phase shift produced by ultrasound. Results: The loop's field was validated and in vivo MR-ARFI measurements confirmed phase contrast. This will enable development of MR-ARFI for focused ultrasound neuromodulation, without associated complications and safety challenges. Impact: MR-ARFI has the potential to guide ultrasound neuromodulation, but its development is hindered by reproducibility and regulatory challenges. We used a DC loop coil to mimic the phase shifts produced by ultrasound in MR-ARFI, to enable MR-ARFI development in vivo.