G.V. Zenkovskiy, A.A. Kornilova, V.M. Naskhletashvili

This work describes computer simulation of laser irradiation propagation results in human tissue (prostate) based on fundamental optical effects such as elastic scattering (static and dynamic), optical fields and photon density waves diffraction and interference. These results are essential both for understanding light propagation process in disperse mediums with absorption and for developing new medical-optics diagnostics and treatment technologies such as photodynamic therapy. We have set the computer model by determining prostate tissue optical properties and setting the bounds between prostate areas with different optical properties. Then we used diffuse approximation of transport equation to simulate light propagation in prostate tissues. To take into consideration PS properties we applied dose distribution equation witch depends on extinction coefficient, photobleaching velocity, total emission current through the tissue and initial PS tissue concentration. To introduce laser emission into the prostate tissue we used brachy therapy method, which includes the following steps: determining the prostate location by ultra sound method, preparing special needles sample according to prostate location, introducing hollow needles into the tissue and inside prostate by ultrasound control, introducing optical fiber into the tissue. The simulation results revealed that the PDT treatment process succeeded while introducing into the prostate 5 optical fiber: 4 of them with 20 mW/cm power, and 1 fiber with 10 mW/cm. All fiber should be introduced into prostate tissue according to determined brachy therapy sample.