Distribution of the laser radiation intensity in turbid media: Monte Carlo simulations, theoretical analysis, and results of optoacoustic measurements

The spatial distribution of laser radiation intensity in turbid condensed media is studied analytically, numerically, and experimentally by the optoacoustic method. Based on optoacoustic measurements and Monte Carlo numerical simulations, the relation is obtained between the optical characteristics of a scattering medium and the position of the maximum of the spatial distribution of radiation intensity in the medium. It is shown that, when the anisotropy factor exceeds 0.8, this dependence has a universal type in the ranges of absorption and scattering coefficients typical for biological tissues. The method is proposed for measuring the extinction and absorption coefficients in light scattering media from the temporal shape of an optoacoustic pulse detected in relative units. An approximate method for solving a radiation transfer equation is verified, and the regions of application of the P₃ and P₅ approximation are established.