Development and Application of Optical Coherence Tomography for Detection of Cerebral in Vivo

Cerebral edema is a condition characterized by a net increase in brain water content. Typically water content is tightly regulated in the brain. However this balance can be disrupted by a number of conditions including traumatic brain injury (TBI), tumor and ischemia and lead to brain swelling, raised intracranial pressure (ICP) and secondary damage that greatly increases the morbidity and mortality associated with these conditions. Intracranial pressure is the most common method for detecting and monitoring cerebral edema in vivo. However, this technique is only capable of providing a global assessment of brain water content and is unable to detect cerebral edema early in its development. The goal of the work presented here is to develop optical coherence tomography (OCT) as a tool for detecting cerebral edema in vivo. OCT is an optical imaging modality capable of producing cross-sectional images of biological samples with micrometer resolution. This work begins by studying an in vivo global edema model with OCT and analyzing the change in the depth-resolved attenuation coefficient. Results demonstrated that the attenuation coefficient decreases due to edema. Additionally, decreased blood flow caused by severe brain swelling was also observed. Next, a focal model of edema is explored in a TBI mouse model. Scattering changes correlated with bleeding and edema formation were observed around the impact site. Lastly, OCT system modifications are described for creating a differential absorption-OCT system designed to increase the OCT signal sensitivity to water in particular, by using the absorption properties of water to determine local water content in the tissue. Preliminary results are presented. Overall the results of this work demonstrate that OCT is sensitive to changes in scattering and absorption caused by cerebral edema and highlight the potential of OCT for in vivo cerebral edema detection and monitoring in a spatially resolved manner