Oral cancer is the 16th most common cancer worldwide. It commonly arises from painless white or red plaques within the oral cavity. Clinical outcome is highly related to the stage when diagnosed. However, early diagnosis is complex owing to the impracticality of biopsying every potentially premalignant intraoral lesion. Therefore, there is a need to develop a non-invasive cost-effective diagnostic technique to differentiate non-malignant and early-stage malignant lesions. Optical spectroscopy may provide an appropriate solution to facilitate early detection of these lesions. It has many advantages over traditional approaches including cost, speed, objectivity, sensitivity, painlessness, and ease-of use in clinical setting for real-time diagnosis. This review consists of a comprehensive overview of optical spectroscopy for oral cancer diagnosis, epidemiology, and recent improvements in this field for diagnostic purposes. It summarizes major developments in label-free optical spectroscopy, including Raman, fluorescence, and diffuse reflectance spectroscopy during recent years. Among the wide range of optical techniques available, we chose these three for this review because they have the ability to provide biochemical information and show great potential for real-time deep-tissue point-based in vivo analysis. This review also highlights the importance of saliva-based potential biomarkers for non-invasive early-stage diagnosis. It concludes with the discussion on the scope of development and future demands from a clinical point of view.
Intra-partum hypoxia is the principal cause of death for every 2 in 10000 infants. Monitoring hypoxia during child-birth will not only prevent infant mortality, but also help prevent cerebral palsy in 10-20% of the surviving babies. Current monitoring techniques either use an indirect biomarker (heart-rate in cardiotocograph) or measure downstream biomarkers intermittently and invasively (fetal blood sampling). For complete fetal wellbeing monitoring, a continuous non-invasive assessment of multiple biomarkers is needed during birth. To address this gap we are developing a noninvasive, continuous sensor based on long wavelength near infrared (LW-NIR) spectroscopic technique for the detection of fetal hypoxia through multiple biomarkers. For specific hypoxia assessment we have identified key optical spectroscopy compatible biomarkers from a list of various biomarkers effected in the physiological processes leading to the development of hypoxia. The key biomarkers identified arecytochrome-C oxidase, oxygenated and deoxygenated hemoglobin, lactate, pyruvate and pH in the connective tissue in presence of other interferences such as lipids, proteins and other sugars. To translate these biomarkers into a viable diffuse-reflectance probe we assessed the light-tissue interaction in the low-scattering, water-absorption dominated LW-NIR window of 1350-2500 nm using Monte Carlo photon migration model and experimentally verified the penetration depth achievable in fetal tissue phantom to ~0.5 mm, only targeting the capillary bed.
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