Multifrequency Nd:YAG laser application for tumor fluorescence diagnosis

A computerized fiber-optic spectrofluorometer based on a multifrequency Nd:YAG laser ((lambda) equals 355, 440, 532 and 660 nm, f equals 25 Hz, E equals 1 - 10 mJ, (tau) equals 12 ns) for tissue fluorescence registration in vivo and ex vivo has been developed. The less intensive fluorescence from a tumor of Sarcoma-45 bearing animal model in comparison with the surrounding normal tissue was observed at the spectral region around 450 nm. The influence of reabsorption, energy transfer and other physical factors on tumor fluorescence, sensitized by Photohem (hematoporphyrin derivative), disodium salt of fluorescein (FL) and chlorin e6 (Chl) was investigated. The pharmacokinetic behavior of Chl in different organs and tumors of the animal models has been estimated. The most intensive Chl fluorescence of tumor tissue was observed at 18 hours after photosensitizer injection. The maximum of the tumor-to-healthy tissue ratio of fluorescence was reached 10 at 27 hours after pigment injection. The fluorescence spectra from different types of human tumors after i/v injection with FL or topical application of ALA were studied. A simple model of Nd:YAG laser system for tumor fluorescence diagnosis has been elaborated. Advantages of the laser fluorescence diagnosis of malignant tumors by solid state multifrequency Nd:YAG laser and the increase in accuracy and specificity of this method is discussed.