Experimental evaluation of a prototype cylindrical section ultrasound hyperthermia phased-array applicator

Area of Science:

• Medical Physics
• Biomedical Engineering
• Acoustics

Background:

• Hyperthermia therapy utilizes heat to treat diseases, often requiring precise energy delivery.
• Ultrasonic phased arrays offer potential for non-invasive, focused thermal treatment.
• Controlling ultrasonic energy deposition is crucial for therapeutic efficacy and safety.

Purpose of the Study:

• To design and construct a prototype cylindrical ultrasonic phased-array applicator for hyperthermia.
• To verify the applicator's ability to focus ultrasonic energy at specific points.
• To investigate the generation of shifted and multiple focal patterns using pseudoinverse method.

Main Methods:

• A 64-element, 75-degree cylindrical-section ultrasonic phased-array applicator was designed and built.
• Focusing capabilities were tested in a water medium.
• Pseudoinverse pattern synthesis was used to generate excitation vectors for shifted and multiple foci.
• Experimental single and multiple-focus patterns at 500 kHz were measured and compared to theoretical predictions.

Main Results:

• The applicator successfully focused ultrasonic energy at its geometric focus.
• Shifted and multiple focal patterns were generated as predicted by the pseudoinverse method.
• Experimental results closely matched theoretical models for both single and multiple foci.
• The main beam's focus was largely insensitive to phase and amplitude errors in element velocities.

Conclusions:

• The developed ultrasonic phased-array applicator is capable of precise energy focusing for hyperthermia.
• The pseudoinverse method effectively controls focal patterns, allowing for therapeutic flexibility.
• The system demonstrates robustness against element errors, maintaining acceptable sidelobe levels for clinical use.