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Near-Infrared Spectroscopy (or NIRS) is an optical technique that uses near-infrared (NIR) light that can penetrate deep into the tissue. NIR light is transmitted to the head, non-invasively most often with the use of fibre optics. The collected, reflected NIR light from as deep as the cortex of the brain has been attenuated due to absorption of the oxygen dependent chromophore in the blood, the hemoglobin. NIRS most often measures the reflected NIR attenuation at a couple of wavelengths, to quantify the concentration of the oxygenated and deoxygenated hemoglobin ([HbO2], [HHb]) and provide information about the brain oxygen levels. Of particular interest are the changes in brain oxygenation due to neuronal activity as they can provide us with an indirect measurement of brain function. This can be measured with functional NIRS or fNIRS. For several years now we have been developing technology that extend fNIRS instrumentation by allowing measuring hundreds of NIR wavelengths instead of just two. The technique is called broadband near-infrared spectroscopy (or bNIRS). The bNIRS system measures changes in light attenuation, reflected back from the head, over 308 near-infrared (NIR) wavelengths (610nm to 918nm). This allow us to quantify the changes in brain tissue [HbO2], [HHb] and the concentration changes in the oxidation state of cerebral cytochrome-c-oxidase ([oxCCO]). In my talk I will discuss how we have been using bNIRS both in our preclinical and clinical investigations in neonatal hypoxic-ischemic injury to quantify brain injury severity and neurodevelopmental outcome.
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