Numerical investigation of the energy distribution of Low-intensity transcranial focused ultrasound neuromodulation for hippocampus

Yi Huang; Peng Wen; Bo Song; Yan Li

doi:10.1016/j.ultras.2022.106724

Numerical investigation of the energy distribution of Low-intensity transcranial focused ultrasound neuromodulation for hippocampus

Ultrasonics. 2022 Aug:124:106724. doi: 10.1016/j.ultras.2022.106724. Epub 2022 Mar 12.

Authors

Yi Huang¹, Peng Wen², Bo Song², Yan Li³

Affiliations

¹ School of Engineering, University of Southern Queensland, Toowoomba 4350, Australia. Electronic address: Yi.Huang@usq.edu.au.
² School of Engineering, University of Southern Queensland, Toowoomba 4350, Australia.
³ School of Mathematics, Physics and Computing, University of Southern Queensland, Toowoomba 4350, Australia.

PMID: 35299039
DOI: 10.1016/j.ultras.2022.106724

Abstract

Objective: Ultrasonic neuromodulation as a safe and non-invasive brain stimulation method that delivers a low-intensity, focused ultrasound to nervous system tissue in a targeted area of the brain. The objective of this study is to numerically investigate the ultrasound wave propagation and the energy distribution within the brain tissues using customized single element focused ultrasound transducers (SEFT), targeting the hippocampus.

Methods: A high resolution detailed human head model with seven tissue types was constructed from magnetic resonance imaging (MRI). A full-wave finite-difference time-domain simulation platform, Sim4life, was then used to simulate a 3D non-linear ultrasound wave equation to the specific region of interest, the hippocampus. Three customized SEFT were used to test the effect of transducer positions, and another customized transducer was used to compare the sensitivity effect on heterogeneous and homogeneous brain models. Finally, the sensitivity and performance of low intensity focusing ultrasound stimulation were evaluated.

Results: An optimized application of SEFT was customized to deliver 100 W/m² intensity of energy deposition at the hippocampus region. About 85.65% of the generated volume beam was delivered to the targeted hippocampus region and the beam overlap parameter was affected by different transducer positions. Deflection angle changes of SEFT at the range of ± 5% did not have a significant effect on energy delivery and position displacement. Only 0.5% of peak pressure change was observed between heterogeneous and homogeneous brain models. The sensitivity analysis also showed that the sound speed is the most influential acoustic parameter.

Significance: This study demonstrated that ultrasound neuromodulation targeting the depth brain tissue of the hippocampus could be a potential and promising alternative method to some non-acoustic brain stimulation modalities. In the numerical study of ultrasound brain stimulations, ultrasound parameters and the brain model need to be properly determined to simulate the ultrasonic neuromodulations.

Keywords: Deep Brain Stimulation; Neuromodulation; Single-element Focused Ultrasound (SEFT); Ultrasound Numerical Simulation.

MeSH terms

Acoustics
Brain* / diagnostic imaging
Computer Simulation
Hippocampus / diagnostic imaging
Humans
Transducers*