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Tadayon, Parsa

University of British Columbia

Introduction: Low-intensity focused ultrasound (LIFU) is a novel, non-invasive, and highly focal neuromodulation technique that has the capability of modulating region-specific brain activity. There are limited studies with the purpose of quantifying the focality of LIFU for cortical targets and the challenges of such a precise technique to target complex sulco-gyral geometry of the cerebral cortex. Therefore, our objective was to address this gap by conducting a computational investigation of LIFU’s energy distribution when targeting complex sulco-gyral geometry of a clinically significant target such as dorsolateral prefrontal cortex (DLPFC). Methods: Individualized head models segmenting different tissue types such as skin, bone, muscle, gray and white matter were created for 20 subjects using their T1w and T2w MRI. Cortical parcellation was performed to parcel cortical structures into gyri and sulci regions of interest for each subject. Targeting trajectories aiming at the left middle frontal gyrus (LMFG) were standardized and selected for each subject. The energy distribution was computed via BabelBrain acoustic software simulation. The volumetric measurements were computed for LMFG, left middle frontal sulcus (LMFS) and the LIFU beam. Results: The study revealed significant variability in the cortical geometry of the DLPFC among subjects, with the LMFG being approximately five times larger than the LMFS on average. The LIFU beam was orders of magnitude smaller than LMFG and LMFS, presenting challenges for reliable targeting. Overlap analysis showed a larger portion of the beam reached the LMFG, with variations depending on the threshold. Interestingly, despite its smaller size, a higher percentage of the LMFS was covered by the beam. Significant inter-subject variability was observed for overlap, underscoring the complexity of LIFU application in neuromodulation. Conclusions: We provided a computational analysis of the challenges associated with targeting the highly complex sulco-gyral geometry of the human cerebral cortex using LIFU. The results demonstrate the challenges of LIFU in achieving consistent and reliable targeting of large, highly variable and complex cortical regions due to its high focality. Additionally, we demonstrated the potential of the quantification methods provided to be integrated into the LIFU treatment planning.

Text

2024-10-08

Attribution-NonCommercial-NoDerivatives 4.0 International

http://hdl.handle.net/2429/89355

Biomedical Engineering

University of British Columbia

UBCV

http://creativecommons.org/licenses/by-nc-nd/4.0/