Characterization of changes in therapeutic ultrasound transducer performance over time using the angular spectrum...

Area of Science:

• Medical Imaging and Instrumentation
• Acoustic Engineering
• Ultrasound Technology

Background:

• High-intensity focused ultrasound (HIFU) transducers are crucial for therapeutic applications but susceptible to defects and degradation.
• Current quality assessment methods for HIFU transducers are limited, focusing only on bulk physical changes.
• Reliable methods are needed to evaluate transducer integrity and performance for safe and effective treatments.

Purpose of the Study:

• To develop and validate a novel method for detecting defects in HIFU transducers.
• To assess the pressure distribution at the transducer surface using the angular spectrum method.
• To evaluate the efficacy of this method in identifying manufacturing defects and degradation.

Main Methods:

• The angular spectrum method was employed to determine the pressure distribution at the transducer surface.
• Pressure distribution at the focal plane was measured for three therapeutic transducers.
• A back-projection algorithm was used to calculate the surface pressure distribution from focal plane data.
• Various scan window sizes were tested to optimize defect detection resolution.

Main Results:

• One transducer exhibited signs consistent with manufacturing defects.
• A second transducer showed degradation over one year, with partial efficiency loss in one half.
• The third transducer remained stable over the one-year observation period.
• A 40 mm x 40 mm scan window at the focal plane was necessary to detect 6 mm diameter surface defects.

Conclusions:

• The angular spectrum method is a viable and effective tool for assessing HIFU transducer quality.
• This technique can identify subtle defects and degradation not detectable by conventional methods.
• Implementing the angular spectrum method can enhance the reliability and safety of HIFU treatments.