Transfontanelle photoacoustic imaging to study pathophysiology of neonatal braininjury

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PROJECT SUMMARY/ABSTRACT: Preterm and/or low birth weight neonates are at high risk for intracranial hemorrhage (ICH) with an incidence of 30%-35%. Complications result in shunt dependence and long-term changes: post-hemorrhagic hydrocephalus, periventricular leukomalacia, gliosis, and neurological dysfunction. ICH has many causes: traumatic delivery, primiparity or extreme multiparity, and low gestational age at birth. Early detection, classification and diagnosis of ICH is essential to reduce brain injury which often leads to motor (e.g., cerebral palsy), visual or cognitive dysfunction. TransFontanelle Ultrasound Imaging (TFUSI) is a routine diagnostic brain imaging method for infants younger than 6 months, whose skull bones have not completely fused together and have openings between them; so-called ‘fontanelles’. TFUSI is widely used due to its low cost, safety, accessibility, and noninvasive nature. Nevertheless, the accuracy of TFUSI is limited; TFUSI does not detect hemorrhages smaller than 5 mm and does not accurately detect blood in CSF. The low sensitivity of TFUSI to bleed size, location and duration may lead to autopsy findings that reveal conventional TFUSI underdiagnoses ICH in 8–34% of cases. Second stage diagnostic tools like magnetic resonance imaging (MRI), computed tomography (CT), and positron emission tomography (PET) have sufficient sensitivity and specificity to study neonatal intracranial hemorrhage, however, all require moving clinically unstable newborns out of the NICU, sedation with its associated risks (hypotension, hemodynamic changes, or allergic reaction), and have high cost. Moreover, CT uses ionizing radiation and PET requires a positron-emitting radionuclide. Near InfraRed Spectroscopy (NIRS) has poor spatial resolution, especially for the small neonate head, and poor penetration depth. To address several limitations of current clinical neuroimaging, we have developed a novel TransFontanelle Multispectral Photoacoustic Imaging (TFMPI) method to study pathophysiology, and to improve the detection of brain hemorrhage in neonates without the need for sedation, radiation or radionuclides. Our ex vivo preliminary results show the surpassing capability of TFMPI in detection and quantification ICH earlier, with higher sensitivity and specificity than US; and, maps brain perfusion similar to MRI. This technique allows earlier diagnosis and treatment which may circumvent neural complications, and improve functional outcomes from cerebral palsy and cognitive impairments. The long-term goal of this research project is to provide a single, cost-effective, portable, point-of-care diagnostic screening for neonates with potential ICH. Studies outlined in the four aims of this proposal assess the feasibility of TFMPI for detection of ICH in a large animal model, similar in size to a human neonatal brain, with a surgically-induced cranial window that serves as a model for neonate’s fontanelle. Aim 1: To determine the lower limits of sensitivity of TFMPI to detect blood in CSF and its age. Aim 2: To detect intraparenchymal hemorrhages and their age. Aim 3: To measure the brain tissue oxygen saturation. Aim 4: To detect vasogenic edema due to brain blood barrier disruption.