Effective irradiance calculation on irregular surface for photodynamic therapy treatment device

摘要

Port wine stains is a congenital vascular malformation disease, which occurs mostly on the face and neck. Photodynamictherapy is an effective treatment for port wine stains, which utilizes photodynamic reaction between light,photosensitizer and oxygen in the tissue to produce phototoxic substance singlet oxygen to destroy the lesion. However,the irradiance dose is simply described by the irradiance on a specific plane instead of the irradiance on the lesion withcurve shape. The clinician has little knowledge about the effective irradiance value on the lesion, which limits theunderstanding between the effect and the dosage. To get the effective irradiance on the lesion, a two-steps algorithm isproposed in this paper. Firstly, the point cloud data of lesion are constructed, and the normal vector of each point of thepoint cloud is calculated based on the least square method. Secondly, according to the first and second laws of irradiance,the effective irradiance on the lesion can be obtained when the parameters of the light source are available. Severaltypical port wine stains lesions are used to verify the difference between the irradiance on the plane and the lesion. Thealgorithm can not only help the clinician to make the preoperative planning of photodynamic therapy, but also provide amethod for the study on the relationship between the effective irradiance dose on the lesions and the treatment effect ofphotodynamic therapy for port wine stains.