Multi-physics Analysis of Electromagnetic Wave Propagation and Photothermal Heating in Human Tissues at Terahertz and Optical Frequencies

Abstract

We present a custom-built, multi-physics model to investigate electromagnetic wave propagation in extreme random media such as human tissue and study its subsequent photothermal effects. The proposed finite-element model consists of two segments – the first one estimates the intensity distribution along the beam path, while the second calculates the increase in temperature due to the wave distribution inside the tissue. We determine the intensity variation in the tissue using the radiative transfer equation and compare the results with Monte Carlo analysis and existing analytical models. The intensity information is then utilized to predict the rise in temperature with a bio-heat transfer module, powered by Pennes’ bioheat equation. The model is parametric, and we perform a systematic photothermal analysis to recognize the crucial variables responsible for the temperature growth inside the tissue, particularly for terahertz and near infrared optical frequencies. Our numerical model can serve as a benchmark for intrabody communication studies involving complex heterogeneous media.