Transcranial ultrasound focusing with flexible array transducer

Transcranial focused ultrasound (tFUS) is a promising non-invasive neuromodulation technique, but skull-induced aberrations hinder precise focusing. While phased arrays offer improved focusing, their rigid interfaces cannot adapt to complex skull surfaces, leading to phase mismatches and reduced efficacy. This study investigates the potential of a 128-element flexible phased-array ultrasound transducer for precise transcranial focusing through numerical simulations. We simulated a custom-designed 128-channel flexible transducer array conforming to a homogeneous skull phantom model. Using the time reversal method, we calculated element time delays to generate focal spots within the skull. Simulations explored single and multi-focal transcranial focusing at frequencies ranging from 500 kHz to 3 MHz and various depths. Results demonstrate that the flexible array effectively corrects skull-induced beam aberrations across multiple frequencies. The array generates single focal points with full-length half maximum (FLHM) less than 15 mm and full-width half maximum (FWHM) less than 4 mm. For multi-point targeting, it produces two focal points with FLHM less than 20 mm and FWHM less than 8 mm. These findings suggest that the flexible array is an efficient method for tFUS. Future work will involve underwater experiments to validate the simulation results and characterize the transcranial focused acoustic field.