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especially UV-A, and wavelengths greater than 320 nm, induce carcinomatous changes in tissue (19). Using visible light or infrared light would facilitate tissue excitation and would be available in the average neurosurgical suite. This wavelength would also have fewer side effects during a lengthy operation. Infrared light at 800 nm was used for excitation, in this study; future studies might assess different excitation light and the resultant emission. It is possible that other wavelengths may result in higher intensities of emission or none at all. The difference in excitation, wavelength may account for the minion difference in, intensity change from one specimen to the next (3). The disparity between published results and those from the current study may also be the consequence of using non--human tissue, implanted tissue or the processing of the material. This experiment utilizes conditions as close to operating room scenarios as possible.
The absorption intensities were increased in the normal tissue compared to the tumor tissue at 446-460, 531-535, and 620-705 nm. Tumor absorption intensities were increased at 410-440 nm when compared to normal. Tumor reflection was more intense at 343-353, 400-420, 461-476, and 536-540 nm. Normal tissue reflectance was more intense when compared to tumor at 338-342, and 442-453 nm. Figure 3 also shows the ranking of intensity.
The earlier studies from Yuanlong et al (20) excited tissue at 365 nm using a pulsed xenon laser and recorded emissions over 550 to 750 nm. The results showed peak reflectance in only the cancerous tissues at 630 and 690 nm. There were 50 specimens that consisted of stomach, tongue, mandible, esophagus and bladder. The results were 89% reliable. Hematoporphyrin derivative, which was thought to be retained in higher concentrations in the cancerous tissue, was thought to be responsible for the peaks. The results do not account for the natural occurring autofluorescence of the hematoporphyrins in normal tissue, which should fluoresce but only in smaller amounts, thus only the ratio should be higher, there should not be an isolated band in tumor tissue but also a band in the normal tissue.
In colon tissue studies, the reflection amplitude increased from adenomatous to cancerous to normal with a peak around 480-5OO nm. The carcinomatous tissue fluoresced at 635 and to a lesser extent in the 650--700nm region. The difference in intensity reflects the ratio of collagen and epithelial cells (8). Richards-Kortum (13) also demonstrated an increased fluorescence in normal colonic tissue compared to adenomatous. Skin tissue verses tumor tissue reflects more between 510 to 600 nm (13). The fluorescence of tumor sera has intensities at 325 and others around 300 340 (16). Normal bronchus fluorescence peaks 510, 555 and 600nm, carcinoma 512, 530, 570 & 660mn (7). Breast & lung cancer can be differentiated by the increase reflectance at 340 and 440 nm. (15). The changes in the spectra intensities from normal to neoplastic may be due to the decreased in NADH and pyridoxal 5' phosphate. The peak emission at 635 and 660-700 in adenocarcinoma may be (Continued on page 134)
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