One-dimensional phased array with mechanical motion for conformal ultrasound hyperthermia

Area of Science:

• Medical Physics
• Biomedical Engineering
• Oncology

Background:

• External ultrasound hyperthermia aims to elevate tumor temperatures for therapeutic effect.
• Achieving conformal heating of the planning target volume (PTV) while sparing surrounding healthy tissue is a significant challenge.
• Current methods often struggle with precise temperature distribution and acoustic window limitations.

Purpose of the Study:

• To investigate the feasibility of conformal heating using a phased array transducer with integrated mechanical motion for external ultrasound hyperthermia.
• To develop a system capable of dynamic focusing and enlarging the acoustic window for improved heat deposition.
• To optimize power delivery for precise thermal coverage of the planning target volume (PTV).

Main Methods:

• A one-dimensional phased array transducer mounted on a rotating shaft was employed.
• The system utilized dynamic focusing with multiple focal spots to target the PTV.
• An iterative gradient descent method determined optimal power weightings for focal spots to achieve conformal heating.
• The shaft and phased array rotation enlarged the acoustic window, preventing overheating of intervening tissues.

Main Results:

• Simulations demonstrated the ability to achieve conformal heating for various tumor shapes.
• Over 95% of the PTV reached temperatures above 43°C.
• The volume of overheated tissue outside the PTV was less than 25% of the PTV volume.
• The combined electrical focusing and mechanical motion approach proved effective.

Conclusions:

• The proposed method of combining phased array transducer mechanical motion with electrical focusing is feasible for conformal ultrasound hyperthermia.
• This technique successfully enlarges the acoustic window and provides dynamic focusing capabilities.
• The system demonstrates significant potential for precise and effective thermal therapy in oncology.