Dynamic regulation of transcranial acoustic focusing based on a focused sector transducer array

Due to the properties of non-invasive, high spatial-resolution, and deep penetration depth, transcranial focused ultrasound stimulation shows unique advantages in precise neural modulation in deep brain nuclei. However, the precision and effectiveness of neural stimulation, realized by large-scale phased arrays, single-element focused transducers, and acoustic lenses, are seriously impacted by the obvious energy attenuation, field distortion, and focus deviation, due to the heterogeneity and complexity of the skull. Hence, the development of a flexible and efficient regulation scheme for transcranial acoustic focusing using a simple array of fewer sources shows its great significance. A dynamic regulation method for transcranial acoustic focusing and precise positioning is proposed based on the phase modulation for a focused array of limited sector transducers. The theoretical model of transcranial acoustic propagation in complex media is constructed. The field distortion and focus deviation caused by the cranial thickness, curvature, and deflection are investigated. Additional phases for sector sources calculated through the time-reversal algorithm are used to compensate the focus deviation. The accurate correction of transcranial acoustic focusing in an acceptable radial offset within 1.75 mm is demonstrated by the experimental measurements using an 8-element focused sector array. The proposed method offers advantages of low cost, efficient focusing, simple structure, flexible regulation, and easy implementation, and it is expected to increase the accuracy of transcranial focusing with improved safety and efficiency for neural modulation, exhibiting significant application potentials in neural therapy.