Multifrequency transcranial focusing based on acoustic lensing

Abstract

Transcranial focused ultrasound (tFUS) possesses significant advantages such as non-invasiveness and high tissue penetration depth, making it a promising tool in the field of brain science. Acoustic holographic lenses enable the manipulation of sound fields through phase modulation, providing a low-cost and convenient approach to realize transcranial focusing. Acoustic holographic lenses have been successfully utilized for precise transcranial focusing in live mice to open the blood-brain barrier and for neural modulation, which shows considerable application potential. However, existing transcranial acoustic holographic lenses can only be driven by specific ultrasound frequencies and focus on predetermined locations, which restricts the flexibility in complex applications. To address this issue, this study establishes a multi-frequency transcranial focusing method based on acoustic holographic lenses to enhance its adaptability within the field of tFUS. By integrating acoustic holographic lenses designed for different focal positions at various frequencies, we generate multi-frequency acoustic holographic lenses suitable for transcranial focusing and conduct experiments to evaluate their performance. In simulations, for single-focus tasks, the PSNR of the proposed method achieves 32.16 dB and 40.18 dB under 1 MHz and 2 MHz ultrasound excitation; for multi-focus tasks, the PSNR values are 29.39 dB and 39.89 dB, respectively. In experiments, for single-focus tasks, the PSNR values of the proposed method are 27.48 dB and 32.33 dB under 1 MHz and 2 MHz ultrasound excitation; for multi-focus tasks, the PSNR values are 23.30 dB and 32.17 dB, respectively. These results demonstrate that the multi-frequency transcranial acoustic holographic lens can effectively modulate the sound field under varying ultrasound frequencies and create high-quality focal points at different locations behind the skull, which significantly enhances the application flexibility of transcranial acoustic holographic lenses.