Jean-Francois Aubry | Searcharxiv

arXiv2026

Impact of Phase Unwrapping on Multitarget Acoustic Lenses for Transcranial Holography

Acoustic lenses have been introduced recently to compensate for the phase distortions induced by the propagation across a human skull for ultrasonic deep-brain stimulation in humans. In this study, we present bifocal lenses that compensate for human skull aberrations and allow simultaneous targeting of multiple structures deep in the brain. We investigated the impact of phase unwrapping in the design of the lenses and how this process improves the distribution of pressure produced in N=5 human skulls for two different spatial arrangements of the targets. The results show that unwrapping the phase computed during the design increases the fidelity of the pressure field generated across the human skulls. The spatial precision is on average improved by 73%, and out of target energy deposition is on average reduced by 58%. The results presented in this study highlight the importance of phase unwrapping to optimize the safety and efficacy of future transcranial ultrasound stimulations targeting multiple regions.

physics.class-ph↗

arXiv2022

Benchmark problems for transcranial ultrasound simulation: Intercomparison of compressional wave models

Computational models of acoustic wave propagation are frequently used in transcranial ultrasound therapy, for example, to calculate the intracranial pressure field or to calculate phase delays to correct for skull distortions. To allow intercomparison between the different modeling tools and techniques used by the community, an international working group was convened to formulate a set of numerical benchmarks. Here, these benchmarks are presented, along with intercomparison results. Nine different benchmarks of increasing geometric complexity are defined. These include a single-layer planar bone immersed in water, a multi-layer bone, and a whole skull. Two transducer configurations are considered (a focused bowl and a plane piston), giving a total of 18 permutations of the benchmarks. Eleven different modeling tools are used to compute the benchmark results. The models span a wide range of numerical techniques, including the finite-difference time-domain method, angular-spectrum method, pseudospectral method, boundary-element method, and spectral-element method. Good agreement is found between the models, particularly for the position, size, and magnitude of the acoustic focus within the skull. When comparing results for each model with every other model in a cross comparison, the median values for each benchmark for the difference in focal pressure and position are less than 10\% and 1 mm, respectively. The benchmark definitions, model results, and intercomparison codes are freely available to facilitate further comparisons.

physics.comp-ph↗