Document Type : Original Research
Authors
1 School of Information Science and Engineering, Changsha Normal University, Changsha 410100, China
2 School of Information Science and Engineering, Xinyu University, Xinyu, 338004, China
Abstract
Background: High-intensity focused ultrasound (HIFU) therapy is an effective minimally invasive treatment technique.
Objective: This work aimed to present a theoretical foundation for transient cavitation control in HIFU treatment and investigate cavitation bubbles in multi-frequency ultrasound.
Material and Methods: In this theoretical study, the nonlinear vibrations of bubbles in different mediums (water, urine, kidney, and muscle) were simulated using Gilmore-Akulichev and modified Keller-Miksis equations. The dynamic changes of bubble radius during irradiation by multi-frequency combined ultrasound were analyzed, and the effects of multi-frequency ultrasound combinations and frequency differences on the maximum and minimum values of bubble expansion radius and bubble collapse time were investigated.
Results: At the same highest frequency, the triple-frequency produced the largest bubble expansion radius (Rmax) while the single-frequency resulted in the smallest bubble expansion radius (Rmin). At the same lowest frequency, the single-frequency had the biggest bubble expansion radius and the triple-frequency had the smallest bubble expansion radius. Compared to the combination with a large frequency difference at high frequency, the triple-frequency combination with a small frequency difference at low frequency exhibited a noticeably larger Rmax, but Rmin showed the opposite behavior. Rmax/Rmin decreased for the same ultrasonic combination when the medium viscosity increased. The bubble expansion radius ratio Rmax/Rmin was positively correlated with the bubble collapse time.
Conclusion: There was a strong correlation between the frequency difference and the multi-frequency ultrasound combination and the maximum and minimum values of the cavitation bubble radius and the collapse time.
Keywords
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