Thermal damage analysis in tissue caused by electromagnetic radiation using space-time collocation method

Over the past half-century, the usage of external heat sources in medical applications has increased substantially. Controlling heat damage is essential for ensuring the efficacy of the treatment. Living tissues are highly non-homogeneous; hence, it is important to take into account the effects of local non-equilibrium on their thermal behavior. In the present study, two- and three- space dimensional time-space fractional single-phase-lag (SPL) and dual-phase-lag (DPL) models for bio-heat transfer in tissue are considered to study the thermal damage and temperature in tissue caused by electromagnetic radiation as an external heat source. The considered mathematical models are more general and consider non-Fourier as well as non-local effects. We obtain the numerical solution for the models by combining Gaussian RBFs and shifted Chebyshev polynomials in the space and time directions, respectively. The RBFs depend on Euclidean distance, so they can easily be used in multidimensional space domain, and the use of Chebyshev polynomials gives spectral accuracy in time direction. It is also explored how different parameters, such as blood perfusion rate Wb, phase lags τq, τt, and fractional derivatives α, β, affect the temperature distribution and thermal damage in the tissue.

Calculation of Effective Thermal Conductivity for Human Skin Using the Fractal Monte Carlo Method

In this work, an effective thermal conductivity (ETC) for living tissues, which directly affects the energy transport process, is determined. The fractal scaling and Monte Carlo methods are used to describe the tissue as a porous medium, and blood is considered a Newtonian and non-Newtonian fluid for comparative and analytical purposes. The effect of the principal variables-such as fractal dimensions DT and Df, porosity, and the power-law index, n-on the temperature profiles as a function of time and tissue depth, for one- and three-layer tissues, besides temperature distribution, are presented. ETC was improved by considering high tissue porosity, low tortuosity, and shear-thinning fluids. In three-layer tissues with different porosities, perfusion with a non-Newtonian fluid contributes to the understanding of the heat transfer process in some parts of the human body.

Numerical simulation of electromagnetic heating process of biological tissue via time-fractional Cattaneo transfer equation

In order to simulate the heat transfer in the process of hyperthermia, one-dimensional time-fractional Cattaneo heat transfer equation (TFHE) is established. Based on TFHE, the heat transfer model is solved by using finite difference method, because a single layer of biological tissue in vitro is irradiated by electromagnetic energy. The effect of power parameters (energy flux density P₀, tissue attenuation coefficient h) and equation parameters (relaxation time τ_q and fractional order β) on the prediction of temperature simulated by TFHE were studied. Furthermore, comparative studies on TFHE, Pennes and CV are performed and evaluated. In the heating process, because of the existence of relaxation time τ_q, the temperature response of TFHE and CV are later than Pennes, leading to the lower temperature prediction of TFHE and CV than that of Pennes. The shorter the time is, the higher the energy is, and the more obvious the difference is.

A method to predict burn injuries of firefighters considering heterogeneous skin thickness distribution based on the instrumented manikin system

An approach was proposed to predict skin burns during heat exposure based on computational fluid dynamics and Python language. Both uniform and heterogeneous skin thickness distributions of the whole body were considered and significant differences were observed. 100% second-degree burns were reached for the uniform skin model after 4-s flash fire, and maintained during the cooling phase. Third-degree burns occurred for the heterogeneous skin model during fire exposure, and the proportion increased in the cooling phase. Results indicated that the model with uniform skin thickness probably overestimates skin burns in the early stage of fire exposure. The prediction at the latter stage of the model with heterogeneous skin thickness tended to be more serious. Ignoring blood perfusion and dynamic thermophysical parameters of the skin model was the limitation of this study. Nevertheless, this method provides the basis for further advancements in thermal protective ensembles, to enhance occupational safety of firefighters.