为了研究光动力疗法选择性光损伤，采用蒙特卡罗方法，建立了组织中光动力剂量数学模型。得到光动力剂量随组织厚度增加呈指数衰减的结果。光动力损伤是阈值过程，对肿瘤组织造成深层光动力损伤时，更多正常组织受到损伤。光斑半径对对肿瘤组织损伤深度有明显影响。结果表明，适量光敏剂能引起浅薄全面的肿瘤组织光动力损伤，深层光动力损伤伴随正常组织损伤。

The purpose is to provide insight into the issue of photo-damage selectivity in photodynamic therapy. Monte Carlo simulation was performed using different optical property for normal and tumor tissue. The decay of photodynamic dose with depth was approximately exponential. The greater depth of effect of increasing photodynamic dose obtainable in the tumor/normal simulation is clear as the greater depth of completely selective damage is,which has a threshold photodynamic dose for tissue necrosis and is affected by the photo spot size. For typical photosensitizer retention ratios,it is possible to obtain a shallow but entirely selective depth of tumor necrosis,but to obtain deeper tumor necrosis necessarily means some degree of normal tissue damage.