Combination of optical coherence tomography and Raman spectroscopy
The two techniques, optical coherence tomography (OCT) and Raman spectroscopy allow visualization of structural changes of biological samples via cross-sectional images and corresponding spectral responses that represent chemical constituents, respectively. By combining the two modalities, the medical practitioner would be able to obtain a fast OCT scan followed by Raman spectroscopy point measurements as an identification step. This method not only promotes early diagnosis but also is a prelude to a point-of-care medical system. The combined microscopic OCT-Raman device was systematically characterized to assess performance and suitability for investigating non-melanoma skin cancer samples and atherosclerotic plaques. A pilot non-melanoma skin cancer study was conducted within the boundaries of the standard clinical workflow. This limited the total measurement time of ex vivo biopsies to 12- 15 minutes per sample which was sufficient for both modalities. By correlating the results from all sources i.e. microscopic, OCT, Raman spectroscopy, and histopathologic images, it was concluded that the combined device was able to differentiate between diseased and healthy tissue. OCT results correlated well with the gold standard and a general Raman spectral shape for basal cell carcinoma type of skin cancers was concluded. In terms of atherosclerotic plaques early as well as advanced plaques were investigated from ex vivo rabbit and human aorta samples, respectively. Early plaques were represented as bright spots by OCT and Raman spectroscopy revealed their constituents to be triglyceride rich regions. Plaques at a later stage were visualized as arterial blockages with bright inclusions of crystalline calcium deposits which were confirmed by Raman spectroscopy. An attempt to test the miniaturized application of the system, using separate fiber based systems under in vivo conditions on a rabbit model, early plaques were investigated.