Tissue models for RF exposure evaluation at frequencies above 6 GHz

Area of Science:

• Bioelectromagnetics
• Thermal Physics
• Biophysics

Background:

• Radiofrequency (RF) energy above 6 GHz exhibits shallow skin penetration.
• Understanding heat transport in subcutaneous layers is crucial for predicting temperature increases.
• Accurate models require detailed knowledge of skin layer properties and variations.

Purpose of the Study:

• To analyze RF energy reflection, absorption, and power density distribution in skin.
• To model the thermal response of skin and subcutaneous tissues to RF exposure.
• To evaluate the contribution of different tissue layers to surface temperature elevation.

Main Methods:

• Developed anatomically detailed multi-layer models of skin and subcutaneous tissues.
• Estimated absorbed power distribution using electrical properties derived from reflected millimeter wave energy and literature data.
• Applied Pennes' bioheat equation and a modified version to simulate thermal response.

Main Results:

• RF energy deposition is primarily in the skin layer for frequencies above 6 GHz.
• Subcutaneous tissue thermal resistance significantly influences surface temperature increases.
• A simplified 3-layer model effectively demonstrates the impact of subcutaneous layers on surface temperature.

Conclusions:

• Subcutaneous tissue properties play a critical role in determining surface temperature elevation from RF exposure.
• Models developed provide insights into RF energy deposition and thermal effects in skin.
• Findings are relevant for establishing safety standards for RF energy exposure.