Continuous Photoacoustic Monitoring of Neonatal Stroke in Intensive Care Unit

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PROJECT SUMMARY/ABSTRACT Neonatal encephalopathy can arise from fetal hypoxia-ischemia during labor, chronic uteroplacental inflammation, and large cerebral artery embolization primarily arising from dislodgement of a placental thrombus. Because of overlapping clinical presentation, differential diagnosis is often delayed until seizures develop and MRI can be safely performed, a time at which most neuroprotectants are ineffective. Whereas hypothermia is approved for use within 6 hours of birth for hypoxia-ischemia, no treatments have been approved for perinatal arterial ischemic stroke because of the difficulty of definitive diagnosis required for clinical trial stratification at birth. With an estimated incidence of 17-93 per 100,000 live births, the incidence of stroke in the perinatal period rivals the incidence of stroke in adults (17-23 per 100,000). Therefore, a device that could rapidly and reliably identify an area of focal cerebral ischemia soon after birth would have a major impact by enabling the testing of neuroprotectants at an early therapeutic time window that would maximize efficacy. The Brimrose Technology Corporation, partnering with Johns Hopkins University, propose a photoacoustic helmet (PAH) device that can be safely deployed at the bedside in the neonatal intensive care unit to 1) continuously monitor and rapidly identify at-risk neonates, shortly after birth, rapidly allowing them to be triaged to therapy; 2) monitor the progress of therapy; and 3) provide prognostic information to the parents of newborns at risk for life-long brain injury. The PA imaging mechanism is a purely hybrid mechanism, providing rich optical absorbance contrast of tissue oxy- and deoxyhemoglobin through intact scalp and skull. A proof-of-concept of detecting decreased tissue oxyhemoglobin in a 1 cm-induced experimental stroke has been demonstrated with standard laboratory PA laser light source and clinical ultrasound detector. Our goal is to incorporate safer light-emitting diodes (LEDs) and more sensitive ultrasound detectors configured in a neonatal helmet to localize cortical regions of low oxygenation in the newborn. In the proposed Phase-I STTR, we will develop fundamental hardware and software components for effective integration. Aim 1 - Software for safe PAH imaging at high contrast resolution, including deep neural network and optimal spectral unmixing techniques to enable a safe and high-speed LED-based PAH system. Aim 2 - Hardware for modular PAH system, including a fiber-coupled Brimrose ultra-sensitive multi- bounce laser microphone and optimal modular unit design for a PAH imaging at high spatial-temporal-spectral resolution through intact scalp and skull. Aim 3 - Framework for modular PAH system integration, enabling a robust integration of modular units in a PAH system with rigid-body tag registration using optical tracking, in which different neonatal head shapes and need for different imaging specifications can be accommodated. The Phase-I milestone is detection of the full blood O2 saturation range at <10 mm full-width-half-maximum in the transverse plane and 5 mm sensing depth through ex vivo neonatal piglet skull + scalp sample with an integrated set of hardware and software packages, allowing preclinical validation studies to proceed in Phase II.