Direct-coupled interstitial ultrasound applicators for simultaneous thermobrachytherapy: a feasibility study

Area of Science:

• Biomedical Engineering
• Medical Physics
• Oncology

Background:

• Simultaneous thermal therapy and brachytherapy offer enhanced cancer treatment efficacy.
• Existing interstitial heating technologies have limitations in heating radius and control.
• Need for advanced applicators compatible with brachytherapy radiation sources is critical.

Purpose of the Study:

• To design and evaluate novel interstitial ultrasound applicators for simultaneous thermobrachytherapy.
• To assess the heating capabilities and control of these direct-coupled interstitial ultrasound applicators (DCIUA's).
• To compare the heating effectiveness of DCIUA's with existing thermal therapies.

Main Methods:

• Development of multielement piezoceramic tubular radiators with integrated thermocouple sensors.
• Design of applicators with biocompatible coatings and a catheter compatible with remote afterloaders.
• Theoretical simulations of acoustic power deposition and temperature distributions.
• Experimental measurements of acoustic efficiency, beam distribution, and in vivo thermal dosimetry.

Main Results:

• DCIUA's achieved 60-65% acoustic efficiency with uniform, collimated beam distributions.
• Simulations and in vivo measurements confirmed effective heating radii of 1-1.5 cm.
• Therapeutic temperature rises were controllable and consistent with simulations.
• Heating radius exceeded that of thermal conduction and RF heating technologies.

Conclusions:

• Direct-coupled ultrasound applicators are practicable for simultaneous thermobrachytherapy.
• These applicators provide more adjustable heating patterns compared to current techniques.
• The DCIUA's facilitate the insertion of radiation sources without active cooling, enabling combined treatment modalities.