SIMPLIFIED APPROACHES TO RADIATIVE TRANSFER SIMULATIONS IN LASER-INDUCED HYPERTHERMIA OF SUPERFICIAL TUMORS

A promising approach to the treatment of superficial human cancer is laser-induced hyperthermia. The correct choice of the parameters used for the treatment planning should be based on modeling of both radiative transfer and transient heating of human tissues, which will allow predicting the thermal conversions in the tumor. In this paper, we focus on radiative transfer modeling, which should be as simple as possible for implementation into a combined heat transfer model. In general, the well-known P-1 approximation is known to be sufficiently accurate in calculations of the absorbed radiation power distribution. At the same time, errors in this approximation may increase in the case of external irradiation, and thus it needs to be examined by comparison with direct Monte Carlo simulation. A computational study with realistic geometrical and optical parameters of the problem undertaken in this work showed that the P-1 approximation considerably underestimates the intense absorption near the body surface in comparison with the direct Monte Carlo solution. At the same time, it has been shown that a one-dimensional solution for radiative transfer can be used as a valid approach due to intense scattering of radiation by tissues. As a result, the modified two-flux approximation is recommended as a component of the multidimensional combined heat transfer model for soft thermal treatment of superficial tumors.