PROBLEM TO BE SOLVED: To provide a method for accurately simulating a cumulative concentration of singlet oxygen that is generated when applying exciting light in a photosensitive material existing in tumor tissue in PDT therapy.SOLUTION: A method for simulating a cumulative concentration of singlet oxygen includes: a step (a) of acquiring the exciting light intensity data in tumor tissue by simulation using the Monte-Carlo code； a step (b) of acquiring a fading factor of the photosensitive material, the singlet oxygen creating photochemical yield, the photosensitive material concentration in the tumor tissue, and the molar absorptivity of the photosensitive material； and a step (c) of simulating the cumulative concentration of the singlet oxygen generated from the photosensitive material in the tumor tissue. The simulation method with the steps (a)-(c) is used, and the cumulative concentration of the singlet oxygen generated when applying the exciting light in the photosensitive material existing in the tumor tissue can be simulated accurately.SELECTED DRAWING: Figure 1
