| Photodynamic therapy (PDT) is a therapeutics that the cell of target tissue is killed by reactive oxygen species(ROS) produced by photo dynamic reaction. When the oxygen existence, the combination of light and photosensitizer causes the generation of reactive oxygen species (ROS), in particular singlet oxygen, superoxide anion and hydroxyl radical, resulting in target tissue death either through necrosis or apoptosis. Direct and indirect evidence supports a prevalent role for singlet oxygen in the molecular processes initiated by PDT.Photodynamic dose(PDD) mainly used to describe the effect of PDT, and its numerical size is based on the concentration of photosensitive drug, power of light, effect of photobleaching and concentration of Oxygen in tissue etc.PDD have a safe threshold in the process of photo dynamic.If PDD is greater than threshold, the normal tissue will be killed.If PDD is less than threshold,the tumor will not be killed compelely. Therefore, the study of distribution of PDD in tissue and effective damage threshold is not only a part of basical study of PDT, but also provide a reference to the clinic.This paper includes the following content.1. basic principle and research progress of PDT is introduced.2.The methmetical model of tumor is established.The distribution of light is simulated by Monte carlo method.The distribution and diffusion photosensitizer and Oxygen is described by Fick's secondary low.Influence to the disribbution of photosensitizer of photo bleaching is study by secondary dynamic equition of photo bleaching.3.Study the distribution of PDD in tissue,and show the curlve of distribution of PDD in tissue.4.Study PDD's influence to the photo dynamic damage by experimentalof 5ALA-PDT to leukemia cell. |
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