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due to the endogenous porphyrins (13). Tsai et al (3) demonstrated a minimal increased fluorescence in normal brain tissue compared to glioma at 470 nm. Their spectra for the two tissues were almost the same. Details of the experiment were not disclosed therefore further comment couldn't be made. However, this study was conducted in the rat and used implanted glioma tissue.
Additional investigations utilize infrared light. This has the advantages of requiring smaller amounts of specimen and allowing for more exact quantification. The spectrums are narrow lines, they do not depend upon natural fluorescence and they are the molecular vibrational fingerprints. However, other than its use for excitation, its reflectance and absorption determination would be limited in the operating suite without specialized equipment such as a spectrophotometer. In human basal cell carcinoma (BCC) Wong et al (21), demonstrated an increased intensity at 972 cm-1. In the infrared region reflectance is reported as the "wave number, which is the reciprocal of the wavelength. Thus the wavelength of 972 cm-1 would be 10,288 nm, which is far beyond 700 nm, the end of visible light. The BCC displayed increased hydrogen bonding of the phosphodiester group of nucleic acids, decreased hydrogen bonding of the C-OH groups of proteins, a decreased intensity ratio between the CH3 stretching and CH2 stretching bands and accumulation of unidentified carbohydrates. Similar changes in hydrogen binding and phosphodiester group, as well as a shift in the band at 1082 cm-1 to i086 cm-1 and another weak band at 991 cm-1, were found by Rigas et al (22 and 23) in colorectal cancer. Wong et al (11) noted additional changes in cervical tissue at 1025, 1047, 1082, 1244, 1155, 1303 and 970 cm-1 and shifts at 1082, 1155 and 1244 cm-1. The recent work by Liu et al (12) produced comparable results as well as differences in the ratio of bands at 1657/1445 cm-1 and nearby which corresponded to the C-N stretching. Infrared spectroscopy can measure changes in tissue on a molecular basis thereby qualitating tissue even at the submicroscopy level. This has opened the gates for more advanced deliberations. To date these studies require advanced and costly technology.
Figure 4 lists the consolidated wavelengths of tumor and normal tissue fluorescence as reported in the literature. There is a range of fluorescence of these non-neural tissues. The results in this study correspond to the reflection, of each type of tumor.
Based upon the available data in the literature the peak emissions of the tumor tissue correspond to increases in trytophan at 348 nm, and NADH & NADPH at 465 (15 and 24). This is different from other experiments, which show a decrease in NADH in the non-neural tumor tissue. The remainder of the peaks does not coincide with other known fluorophores. Not all samples may be identical because of the individual variability in tissue, biochemical content, density and equipment. This may also be due to tissue attenuation of the emitted fluorescence due to absorption and/or scattering. The spectroscopic properties of fluorophores are (Continued on page 135)
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