Comparison of Waveform Modulation Methods Used in Pattern Interference Radiation Force Neuromodulator

Transcranial focused ultrasound is one of the most preferred non-invasive neuromodulation methods owing to its high penetration depth and resolution. Although the exact mechanism has not been elucidated, mechanical stress caused by acoustic radiation force is considered to be important in ultrasound neuromodulation. The ultrasound neuromodulation method using the pattern interference radiation force proposed in a previous study efficiently generates compression and tensile forces; however, it is difficult to improve the resolution. This paper presents an optimization method for calculating arbitrary input pressures to improve the resolution of mechanical stresses caused by pattern interference radiation forces. The optimized result was verified by calculating the time-averaged radiation force and stress tensor generated in the tissue via numerical simulation. Simulation results show that it is possible to generate a single compressive or tensile stress at a specific location within the tissue.