Why we should care about soft tissue interfaces when applying ultrasonic diathermy: an experimental and computer...

Area of Science:

• Biomedical Engineering
• Acoustics
• Thermal Physics

Background:

• Therapeutic ultrasound aims to generate heat in tissues.
• Standard protocols often overlook absorption and reflection at tissue interfaces.
• Understanding interface effects is crucial for optimizing ultrasound therapy.

Purpose of the Study:

• Investigate heat generation at tissue interfaces near the transducer and bone.
• Utilize computer simulations and tissue-mimicking phantoms.
• Assess the impact of soft tissue and bone interfaces on ultrasound heating.

Main Methods:

• Employed physiotherapeutic ultrasound equipment for irradiation.
• Used two-layer soft tissue phantoms, with and without a bone layer.
• Monitored temperature with thermocouples and employed COMSOL® for computational modeling.

Main Results:

• Observed a significant temperature rise (42°C) at 10mm depth, consistent with or without bone.
• Experimental results showed a 3°C divergence from simulations.
• Heating near the bone layer was less than predicted, potentially due to convection effects not included in simulations.

Conclusions:

• Soft tissue interfaces play a critical role in therapeutic ultrasound heating.
• These interface effects warrant greater consideration in treatment protocols.
• Even without immediate bone proximity, soft tissue interfaces impact thermal distribution.