Review Of Fluorescence Diagnosis Using Porphyrins

Tumors can be detected by their increased fluorescence compared to surrounding tissue, several hours after injection of a fluorescent, tumor-localizing compound such as dihematoporphyrin ether. The fluorescence is observed by either a nonimaging photodetector, with appropriate filters, or by an imaging optical system (usually employing an image intensifier because the fluorescence is weak). Excitation is best carried out with a laser, but a filtered arc lamp may be suitable. Instruments differ in the methods of excitation, detection, reduction of background from native fluorescence of tissues, and provision for a whitelight - illuminated reflectance image or other means for guiding and identification of anatomical landmarks. Carcinoma in situ has been detected by a number of these instruments.