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pathologist
The spectrometer used was a Shimadzu UV- Visible recording spectrometer model UV-160, with ability to record in the infrared region. The specimens were each placed in a methacrylate 1.5 cc semi-micro cuvettes (transmission 275 to 800 nm, absorbance +/- 1%) at an optical path of 10 mm. The excitation wavelength was 800 nm. (In the future it may be better to fix the tissue after spectroscopy and send this tissue to pathology to confirm the diagnosis). The absorption spectra between 320 and 800 were recorded over 60 seconds and a print out obtained. Next the first order absorption derivative was recorded. This procedure was repeated for the saline. Several measurements were made with the tissue with and without saline in the cuvette. It was determined that the tissue absorption and reflectance was the same as the spectra in saline after the spectra from saline alone was subtracted.
RESULTS
Figure l a and b demonstrates the spectra of all tumor and all normal tissue. Multiple points at the same wavelength have been omitted.
Figure 2a-e demonstrates the spectra of tumor and normal tissue separated into 100 nm wavelengths for ease of viewing. The spectra of normal saline is subtracted as well as for hemoglobin, (14), leaving the emissions from the tissue alone.
The absorption spectrum of oxyhemaglohin peaks at 280, 350, 420, 540 and 580 nm.
UV<400;violet 400-450;blue 450-500;green 500-550;yellow 550-600;oranqe 600-650; red 650-700; infrared>700.
Tumor tissue absorbs preferentially at 428+/-8 nm, 486+/-10 nm, 528+/-8 nm and 549+/--8 nm. These wavelengths are separating from the normal tissue absorption by greater than 5 nm, the distance needed by the average commercial available narrow bandwidth filter. These wavelengths are in, the violet, blue, green arid yellow. Normal white matter absorbs preferentially at 334+/-4 nm, 620-680 nm with a peak at 640 nm and at 703+/-6 nm. Tumor tissue reflects preferentially at 403+/-10 nm, 477+/-8 nm and 790+/-10 nm. Normal tissue preferentially reflects at 506+/-5 nm and 697+/-6 nm.
DISCUSSION
Past studies (15 and 8) have used the ratio of reflection, intensities at two distinct wavelengths to distinguished tumor from malignant tissue. Ratio fluorometry corrects for distance, angle, surface topography, detection ability and intensity of excitation light (7). However, it is difficult to decide upon which wavelengths to use and the statistical analysis needed. These studies excited the tissue at 280 (16); 325 or 337 (17); 370 (18); and also 430 (13) that were found to be the best wavelength to differentiate normal tissue from neoplasm. As an, excitation, wavelength, ultraviolet light, (Continued on page 133)
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