Photosensitizers, in general, tend to accumulate in neoplastic tissues. The ratio of photosensitizer concentration between tumor and surrounding normal tissue varies with the photosensitizer and the tissue and forms the basis for successful PDT. Selective photosensitizer uptake in vascular, proliferative tissues is used to target certain non-neoplastic tissues, as well as tumors, for destruction. As a rule, it can be stated that practically all photosensitizers that have been studied have a pronounced affinity for non-neoplastic tissues, which are high in reticuloendothelial components. 4
The first attempt at photodynamic endometrial ablation was carried out on ovariectomized rats. Dihematoporphyrin ether (DHE) was taken up by the endometrial layer of the estrogen-primed rat uterus. Photoradiation of the uterine surface 72 hours after DHE administration caused selective coagulation necrosis in the entire endometrium and the inner part of the muscularis. 5 PDT endometrial ablation was also studied in rabbits, which, like rats, have a double uterus, providing a convenient treatment and control uterine horn in each animal. Bhatta et al 6 showed that Photofrin (porfimer sodium) was retained preferentially by the endometrium, with the greatest concentration observed in the stroma. Laser light was delivered using an optical fiber with a diffusing tip inserted in the rabbit uterus. When the uterus was examined after treatment, endometrial necrosis was confirmed and related to the dose of Photofrin. Despite the rabbit’s relatively thin myometrium, there was no full-thickness uterine destruction.