The correlation between bubble-enhanced HIFU heating and cavitation power.

Area of Science:

• Ultrasound Physics
• Biomedical Engineering
• Acoustic Cavitation

Background:

• Bubble presence enhances heat generation via scattering and absorption.
• Inertial cavitation is a primary driver of increased heating in high-intensity focused ultrasound (HIFU).
• Bubble-induced heating can exceed direct ultrasound absorption heating by severalfold.

Purpose of the Study:

• To quantify the temperature rise caused by bubble activity during HIFU.
• To establish a correlation between cavitation signals and bubble-induced heating.
• To explore the use of cavitation signals as a proxy for measuring inertial cavitation heating.

Main Methods:

• Measurements of temperature and cavitation signals during 1.1-MHz HIFU in tissue-mimicking phantoms.
• Correction of measured temperature for primary ultrasound absorption heating.
• Analysis of the relationship between corrected temperature rise and passive cavitation detector output.

Main Results:

• Isolated temperature rise from bubble activity was measured.
• Temperature rise from cavitation correlated strongly with the "cavitation power" measured by a 15-MHz passive cavitation detector.
• The mean square voltage output of the detector served as an indicator of inertial cavitation heating.

Conclusions:

• Bubble-induced heating is a significant factor in HIFU applications.
• Cavitation signal processing offers a viable method for estimating inertial cavitation's thermal contribution.
• This finding supports using cavitation detection for real-time monitoring and control of HIFU thermal effects.