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

Abstract

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 operating at 500 kHz), 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.

BabelBrain: An Open-Source Application for Prospective Modeling of Transcranial Focused Ultrasound for Neuromodulation Applications

“…A recent study found that when using simple tissue masks with homogenized skin, bone, and brain tissue layers, multiple modeling methods, including the one used in this study, produced similar results [7] without needing any additional corrections. However, when using voxel-level properties in a viscoelastic solver, the Q factor models exclusively dissipative effects and scattering effects are introduced by the heterogeneity of the material.…”

“…Angla et al recently presented a thorough and excellent review on this topic [6]. While several modeling approaches have been crossvalidated in simplified numerical settings [7], there are few to none open-accessible complete modeling suites that work in integration with neuronavigation systems to assist FUS-based neuromodulation experiments.…”

Auditory confounds can drive online effects of transcranial ultrasonic stimulation in humans

“…The acoustic properties of sound speed, density, alpha coefficient, and alpha power, as well as the thermal properties of thermal conductivity and heat capacity, were assigned to the skull, scalp, and brain, as reported in Table 1 (Aubry et al, 2022; Hasgall et al, 2022).…”

S.M.A.R.T. F.U.S: Surrogate Model of Attenuation and Refraction in Transcranial Focused Ultrasound

“…We applied the MATLAB-based pseudospectral solver toolbox k-Wave [ 7 ] to perform the simulations(see Aubry et al, 2022 [ 8 ] for comparison to other comparable software). Note that K-wave itself has been extensively validated empirically [ 9 – 12 ].…”