Research on focusing methods and sound field characteristics of transcranial ultrasound focusing

A heterogeneous cranial simulation model is established based on high-resolution CT data, which introduces the acoustic attenuation coefficient of the cranium, and the focus methods and effects of time reversal method of acoustic waves and ultrasonic phased array method in the skull are studied and analyzed. The skull has strong acoustic attenuation characteristics and requires amplitude compensation when using time-reversal method. For a frequency signal of 0.7MHz, the amplitude compensated time-reversal focused acoustic field has narrow main flap width and low flap amplitude, and the acoustic field at the focal point is 8.86dB higher than that of the time-reversal method without amplitude compensation and 7.89dB higher than that of the ultrasonic phased-array focusing method, which has good spatial focusing accuracy and focusing efficiency. By studying the effects of skull attenuation coefficient, sound field focal position, acoustic frequency, transducer array position and orientation on the focused sound field, it was shown that the amplitude compensated time-reversal method has lower partials than the phased array, and the focusing effect at high frequencies is better than the phased array method, the phased array method is more sensitive to the transducer array position and orientation, while the time-reversal transcranial ultrasound focusing has higher robustness to the sound propagation path and incident angle. The time-reversed transcranial ultrasound focusing has higher robustness to acoustic propagation path and incident angle.