Abstract

Objective: High-intensity focused ultrasound (HIFU) is a non-invasive therapy that ablates diseased tissues with high precision. Computational simulations using the Pennes Bioheat Transfer Equation (PBTE) can guide HIFU treatment by predicting temperature distributions and thermal dose volumes. Traditional simulations assume constant thermal and acoustic properties, which may oversimplify tissue behavior. Methods: This study evaluates the impact of integrating temperature-dependent thermal properties (thermal conductivity, specific heat capacity, and perfusion) in finite-difference time-domain HIFU simulations. Three scenarios were simulated: (1) a homogeneous liver with both high- and low-power sonications, (2) a rabbit thigh muscle validated against preclinical MRTI data, and (3) an extended rabbit with temperature-dependent acoustic properties integrated with Hybrid Angular Spectrum (HAS) acoustic simulations. Temperature-dependent models were compared with constant-property models whose data were collected at 25 °C, 20 °C, and 37° C. Results: For high-power sonications in liver tissue, temperature-dependent properties resulted in up to 17.6% and 13% more necrotized tissue compared to constant-property models at 25° C and 37° C, respectively. In low-power sonications replicating mild hyperthermia, liver temperature rises were 17-20% lower due to temperature-dependent perfusion. In rabbit muscle, temperature-dependent models showed up to 18% difference in necrotized tissue, with temperature curves following the trends observed in Magnetic Resonance Thermal Imaging (MRTI) data. Incorporating temperature-dependent acoustic properties increased the predicted necrosis volume by up to 30%. Updating properties every 2.5 seconds maintained simulation accuracy (less than 1% difference in maximum temperature) while reducing computational cost by up to 70%. Conclusion: Integrating temperature-dependent properties in HIFU simulations led to nontrivial changes in temperature profiles and substantially altered necrosis predictions by capturing perfusion shutdown and variations in thermal properties. An effective update interval for acoustic properties to maintain accuracy was not determined, whereas updating thermal properties every 2.5 seconds balanced computational efficiency and accuracy.

Degree

MS

College and Department

Ira A. Fulton College of Engineering; Mechanical Engineering

Rights

https://lib.byu.edu/about/copyright/

Date Submitted

2025-04-15

Document Type

Thesis

Keywords

High-intensity focused ultrasound (HIFU), temperature-dependent properties, acoustic properties, computational modeling, necrosis prediction

Language

english

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Engineering Commons

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