Fetal hypoxic brain injury is the deprivation of oxygen during labour and is associated with up to 60% mortality. The gold standard of fetal monitoring during labour, the cardio tocograph (CTG) and fetal blood sampling are poor at diagnosing hypoxia continuously and non-invasively. Our research is towards developing a non-invasive, continuous hypoxia assessment system using long wavelength near-infrared spectroscopy through a fiber optic based reflectance. Lactate is a key biomarker for hypoxia determination in babies during birth. For successful implementation of this probe, it is required that it detects lactate in maternal environment and in presence of other spectroscopic interferences. In this paper we look at lactate sensing through a liquid phantom containing spectrally interfering components alongside lactate like glucose, urea, triacetin and albumin. Through these experiments we determine the relevant wavelengths and their combination for effective lactate sensing.
In this work, we aim to develop a virtual platform to compare the performance of the different manifestations of photon Time of Flight Spectroscopy namely Direct, Indirect and Interferometric photon Time of Flight Spectroscopy (pToFS). Extending the comparison over a range of scenarios, defined by a matrix of optical properties (dubbed here as Virtual Tissue), allows for the definition of different use cases for each of these techniques. The effect of parameters like temporal drift, exposure time and background noise will also be studied.
KEYWORDS: Short wave infrared radiation, Hypoxia, Fetus, Near infrared spectroscopy, Spectroscopy, Monte Carlo methods, Reflectivity, Sensors, Reflectance spectroscopy, Photon transport, Near infrared
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 are – cytochrome-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.
The Oral Squamous Cell carcinoma (OSCC) is one of the most common and aggressive oral malignancies. Despite all significant advances in medicine, five-year survival rate is still low. This study aims to develop a full scheme for diagnosing oral cancer in early stages by using Raman spectroscopy. Patients undergoing biopsy or histopathological examination will be enrolled in this study. Ex vivo measurement will be carried out using saliva specimens and in vivo analysis will involve measurements taken on healthy and malignant tissue. In the future, this optical diagnostic approach using Raman spectroscopy and SERS can help in improving diagnostic accuracy and the survival rate by affecting the treatment outcome via early stage detection of oral cancer.
Hypoxia assessment needs tools beyond the oxygen measurement. With both transmission and on-the-surface measurements in liquid phantoms, animal, and human samples we show ability of LW-NIR spectroscopy as a continuous monitoring and diagnostic tool.
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