Tissue backscattering dynamics simulation

As usual the tissue optical properties suppose invariable during the measurement interval in most medical diagnostic applications. The last affirmation based on a fact of low radiation intensity, which excludes its influence on the diagnostic process. But recent experimental investigations show that the low level optical fields may stimulate the alteration of the tissue optical state, thus, such an alteration must be taken into account in diagnostic investigations. In present theoretical analysis the biological tissue model was presented as a piecewise heterogeneous semi-infinite medium and Monte Carlo method was used for scattering simulation. We use detail modeling only for upper layers, where the maximum absorption and scattering of the radiation occur. The other part of the tissue was considered to be homogeneous. Every tissue layer was characterized by its own optical properties. According to experimental data the time scale of the tissue optical properties alteration in a low level optical field is about several tens of seconds. The alteration of tissue optical properties occurs first of all due to the changes in bioliquid state (blood state)