Comparing the Influence of Different-Order HIFU Harmonic Superposition on Focal Temperature of Biological Tissue

Introduction: While high-intensity focused ultrasound (HIFU) is widely used for non-invasive tumor ablation, current models fail to account for the cumulative energy contributions of nonlinear harmonics (up to the ۲۵۶th order), significantly limiting treatment precision. This study quantifies the role of harmonic superposition (۱st+۲nd+…+۲۵۶th order) in regulating HIFU-induced focal temperature and establishes an optimized harmonic combination to enhance clinical parameter design.   Material and Methods: A coupled acousto-thermal model, validated against MRI thermometry, was developed by solving the Westervelt equation and Pennes bioheat equation to simulate nonlinear acoustic propagation and transient temperature fields in ex vivo porcine muscle under HIFU irradiation. Results: The ۱st+۲nd+...+۱۲۸th harmonic superposition model achieved <۲.۲% error in focal temperature prediction across all tested power levels (۸۰–۲۰۰ W), with errors of ۱.۶% at ۸۰ W (۴۸.۱۸ °C simulated vs. ۴۷.۹۶ °C measured), ۱.۱% at ۱۴۰ W (۶۶.۰ °C vs. ۶۵.۳۱ °C), ۱.۸% at ۱۶۰ W (۷۷.۷۸ °C vs. ۷۶.۳۸ °C), and ۲.۲% at ۲۰۰ W (۸۲.۲۵ °C vs. ۸۴.۱۱ °C). Mid-order harmonics (۲nd–۶۴th) contributed ۷۵–۸۰% of energy deposition, while high-order harmonics (>۱۲۸th, e.g., ۲۵۶th at ۲۷۶.۴۸ MHz) exhibited severe attenuation (۱۳۵× higher than the fundamental wave). The linear propagation model (fundamental frequency only) underestimated temperatures by ۴.۸-۲۳.۹%, highlighting the necessity of nonlinear harmonic inclusion. Conclusion: This work establishes a harmonically optimized framework for HIFU treatment planning, addressing a critical gap in nonlinear acoustic modeling and enabling safer, precision thermal therapy.

کلیدواژه ها:

High ، Intensity Focused Ultrasound Harmonic Temperature Thermal Therapy Nonlinear