Laser Interaction With Biological Tissues Monte Carlo Study

Biological tissues are a kind of high scattering random media, studies on laser light propagation and distribution in biological tissues play an important role in therapeutics and diagnostics. The main content of this paper includes two parts: part one is the introduction to the studies on laser light propagation and distribution in tissues by Monte Carlo method and part two is the researches on temperature field induced by laser light in biological tissues.The rule of Monte Carlo method is described in detail first. Then the joint of convolution and Monte Carlo is introduced. With convolution, Monte Carlo is used to simulate the interaction between biological tissues with different types of incident light..The features of photon absorption and scattering in tissues are very important issue to the discussion of the feasibility of some novel optical methods for tissue functional imaging, such as photo-acoustic imaging. Under this background, in this paper, a multi-layered model was used to simulate the absorption and scattering features of light in skin, adipose and muscle. The light was perpendicularly incident on the top surface of the model tissue. The absorption distribution was obtained on a plane at a certain depth into tissue. The probability of reflectance, absorption and transmission of photons are discussed with the changing of optical parameters of the tissue. The results showed that most of the photons are absorbed after multi-layered tissue scatterings with about 7.3 percent reflectance (specular reflectance and diffuse reflectance ) from epidermis.Based on the knowledge of optical parameters of biological tissues, we simulated the light distribution and propagation with different types of incidence. The study of diffused reflectance can offer great reference.In the last section, the thermal conductivity equation is introduced, and the temperature distribution induced by laser absorption in biological tissue is given. The effect on steady state temperature distribution by changing of optical parameters is discussed.