- FTIR employs a unique approach to optical diagnosis of tissue pathology based on the characteristic molecular vibrational spectra of the tissue. The architectural changes in the cellular and sub-cellular levels developing in abnormal tissue, including a majority of cancer forms, manifest themselves in different optical signatures, which can be detected in IR spectroscopy. The molecular vibrational modes, which are responsible for IR absorption spectra, are characteristic of the biochemistry of the cells and their sub-cellular components. The biological systems we have studied include adenocarcinoma and normal colonic tissues obtained from the department of pathology at Soroka Medical Center. Our method is based on microscopic IR study of thin tissue specimens and a direct comparison with normal histopathological analysis, which serves as a 'gold' reference. Several unique differences between normal and cancerous intestinal specimens have been observed. The cancerous intestine has weaker absorption strength over a wide region, which includes several significant vibrational bands. The results from microscopic IR absorption spectra from intestinal tissues have also been compared with other biological tissue samples.