Analysis of photon transport in biological tissue and the subsequent heating effects

• This article investigates the photon transport and distribution in tissue and the consequent heating effects linked to that via a combination between RTE and bio-heat transfer equation.
• The coupling between MC and FDM was implicitly to obtain the temperature variation with depth as one selected variation for comparison with the same result obtained by employing MC method directly on the bio-heat equation.
• Temporal and spatial heating distribution was obtained as important parameters in determining the applicability of laser for tissue heating and controlling the heat affected zone.
• Thermal damage and/or rate of thermal damage is analyzed as an important parameter for heating threshold.

Analysis of laser interaction with matter revealed the possibilities of many industrial and therapeutic applications. This research article discusses the theoretical aspects of laser beam interaction with biological tissues. It introduces the numerical analysis of photon distribution and transport in the tissue and its bio-thermal heating effects. The Monte Carlo method has been applied to simulate the variation of photon distribution and photon fluence with the radial distance from the point of interaction as well as laser powers and tissue thickness. For a specific wavelength, the variation of diffuse reflectance with the absorption coefficient was depicted for different values of the anisotropy factor. It has also been used to simulate the bio-heat transfer to obtain the temperature variation with the heating depth. On the other hand, finite difference method (FDM) has been applied to simulate the heating effect resulted from the incident laser beam on the tissue based on Penne's bio-heat equation combined with the obtained photon distribution and transport parameters from the MC method. The heating effect of the laser beam and hence the occurred thermal damage in the tissue was depicted. A linear relationship between the temperature and the rate of thermal damage has been manifested. This result can be used as a threshold reference for various medical applications of lasers.