The concentration of Photofrmn II is needed to determine the dose in photodynamic therapy, and in fluorescence diagnosis of tumors. A method based on fluorescence was devised which shows promise. Diffusion theory was applied in slab geometry with closely spaced excitation and emission wavelengths. A function of the measured radiant energy fluences for excitation and emission, and the depth x, was found that canceled the dependence on depth. A function of the diffusion coefficient and attenuation coefficient was derived from the measured diffuse reflectance. This function compensated for differences in absorption and scattering in different tissues, or a calibration phantom and tissue. Comparisons should be made with the concentration derived in other ways, but the fluorescence method shows promise.
Photochemical reactions are used in photodynamic therapy of cancer and other disease. The cytotoxic agent in photochemotherapy is usually singlet oxygen. Thus measurements of singlet oxygen production or concentration may allow prediction of the biological response. The decrease in fluorescence of L-tryptophan because of reaction with singlet oxygen, the decrease in absorbance of a dye such as RNO subject to secondary oxidation by singlet oxygen, and the decrease in fluorescence of the most common photosensitizer, dihematoporphyrin ether /ester (DHE) because of photobleaching, have been investigated in solutions in vitro. The most promising method for dosimetry and prediction of biological response appears to be the photobleaching of DHE.
An optical phantom of tissue has been devised to simulate the optical properties of typical tissues for research in photodynamic therapy (PDT). The phantom consists of a scatterer (polystyrene-divinylbenzene microspheres) and a absorber (india ink) in distilled water. A set of relevant data for the microscopic optical properties and macroscopic optical parameter of phantom was found. The results obtained approximate the optica1 properties of typical tissues. This optical phantom may duplicate the spatial variation of the radiant energy fluence of typical human tissues at 630nm wavelength in PDT.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.