Ultrasound applicators with internal water-cooling for high-powered interstitial thermal therapy

Area of Science:

• Biomedical Engineering
• Medical Physics
• Thermal Therapy

Background:

• Interstitial thermal therapy utilizes ultrasound (US) applicators for hyperthermia and coagulation.
• Current applicator designs face limitations in heat dissipation, restricting power levels and treatment efficacy.

Purpose of the Study:

• To investigate the efficacy of internal water-cooling for direct-coupled ultrasound applicators used in interstitial thermal therapy.
• To assess the impact of water-cooling on applicator performance, heat transfer, and therapeutic outcomes.

Main Methods:

• Constructed implantable tubular and directional ultrasound applicators with integrated internal water-cooling systems.
• Measured convective heat transfer coefficients and evaluated acoustic intensity and beam distribution.
• Conducted in vivo and in vitro heating trials to assess thermal penetration and coagulation depth.

Main Results:

• Achieved high convective heat transfer (2100-3800 W/m2K) at practical water flow rates.
• Internal water-cooling did not significantly degrade acoustic performance.
• Enabled substantially higher applied electrical power (> 45 W) compared to non-cooled designs.
• Demonstrated improved thermal penetration and coagulation depths (12-20 mm) in biological tissues.
• Directional applicators produced controlled, shaped thermal lesions.

Conclusions:

• Internal water-cooling is a significant advancement for ultrasound interstitial thermal therapy (USITT).
• This technology allows for greater treatment volumes and shorter treatment times.
• It offers potential for treating highly perfused tissues and creating precisely shaped lesions.