Direct methods for characterizing high-intensity focused ultrasound transducers using acoustic streaming

Area of Science:

• Acoustics
• Fluid Dynamics
• Biomedical Engineering

Background:

• High-intensity focused ultrasound (HIFU) requires accurate intensity field determination for therapeutic applications.
• Existing methods, like iterative streaming techniques, can be time-consuming.
• Noninvasive measurement of ultrasound fields is crucial for safety and efficacy.

Purpose of the Study:

• To introduce and validate two novel, direct methods for noninvasively determining the intensity field of HIFU transducers.
• To compare the accuracy and speed of these direct methods against established iterative techniques and hydrophone measurements.

Main Methods:

• The study utilizes the streaming velocity induced in a liquid medium by the absorbed ultrasound beam.
• Differential operations of the Navier-Stokes equations are directly applied to experimentally measured streaming velocity data.
• The direct methods are compared with an iterative streaming method and traditional hydrophone measurements.

Main Results:

• The direct methods provide a significantly faster alternative to iterative techniques for measuring HIFU intensity fields.
• Comparisons showed less than 20% difference between direct methods and iterative techniques at focal intensities of 100-1000 W/cm(2).
• Similar agreement was observed when comparing with low-power hydrophone measurements.

Conclusions:

• The developed direct streaming velocity methods offer a rapid and accurate approach for noninvasive HIFU intensity field characterization.
• These techniques are particularly advantageous in regions where accurate streaming velocity data is available.
• The findings support the use of these direct methods in applications requiring efficient and reliable HIFU field assessment.