Probing phased-array focused ultrasound transducers using realistic 3D in-silico trabecular skull models: A numerical study.

Transcranial focused ultrasound (tFUS) is an emerging neuromodulation technology with transformative potential for brain disease therapies. This study explores how the trabecular structure of the human skull affects the performance of multi-element tFUS transducers. Numerical simulations were conducted using realistic 3D skull models with varying porosities (0%, 50%, and 60%), comparing the pressure fields generated by two geometrically distinct 96-elements phased-array transducers (f-number = 0.8 -transducer 1- and f-number = 1.1 -transducer 2-). Pressure distribution maps and -6dB isosurfaces were analyzed to quantify focal and scattered volumes, as well as focus shifts. Results demonstrate that porous skull models significantly impact the pressure field, introducing scattering and hotspots outside the target area, that are undetectable with non-porous models. Both transducers exhibit focus shifts along the propagation axis, with transducer 2 showing lower selectivity and nearly 450% and 1000% increased scattering compared to transducer 1 in the porous models. These findings emphasize the necessity of incorporating such models in tFUS simulations to improve the accuracy of pressure predictions and device performance. Our results highlight the critical importance of accurately modelling skull porosity in tFUS simulations. Using simplified non-porous models can obscure scattering effects and lead to distorted predictions of transducer performance. This work also demonstrates how generating in-silico porous models with varying porosity allows for testing the reliability and robustness of a numerically designed transducer. It also provides valuable insights into optimizing transducer design ultimately improving target precision while mitigating unintended sonication, laying the groundwork for safer and more effective tFUS therapies.