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Cerebral oxygenation monitoring at early stage of life is a measure of diagnosing hypoxia-induced brain injuries that may otherwise result into severe neurological disorders. Two primary clinical methods (percutaneous insertion of a catheter and insertion of a probe through cranium) used to monitor brain oxygenation are invasive. Therefore, an accurate and non-invasive brain oxygen saturation measurement in neonates is of great significance. In addition, the presence of the optical/acoustic window in neonates, known as fontanelle, provides an opportunity to extract cerebral oxygen saturation from deeper structures within the brain tissue. High sensitivity to oxy and deoxyhemoglobin of photoacoustic (PA) technique enables the non-invasive oxygenation measurement based on spectroscopic analysis at two or more wavelengths. Here, we have utilized a handheld Transfontanelle PA probe to measure brain oxygen saturation in sheep brain in-vivo through surgically induced fontanelle. The rationale of using sheep brains for this study is the similarity in size to a human neonatal brain. The inspired oxygenation level by the animal ranging from 12 to 100% was externally controlled to introduce both hypoxia and hyperoxia. The performance of the PA probe was evaluated by comparing with the gold standard arterial blood gas analyzer results. The extracted oxygenation saturation from Transfontanelle PA strongly correlates with measured value of the blood gas analyzer as compared to pulse oximeter reading. Our results indicate that monitoring of cerebral blood oxygenation can be performed in neonates noninvasively and accurately through the fontanelle.
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