PROJECT SUMMARY/ABSTRACT Congenital heart defects are present in 1.8% of newborns and account for one third of congenital defects. Despite all the research that has been done, 80% of cases have no identifiable causes. Biomechanical factors are known to regulate cardiac development, but the lack of methods to analyze flow in live embryos limits progress in biomechanical studies. Mouse models have revealed much about cardiovascular development, but biomechanical studies are extremely limited as imaging motion in embryonic hearts requires high speed, spatial resolution, and imaging depth. Our lab’s recent advancements in optical coherence tomography (OCT) uniquely meet these requirements for live embryo imaging through the heart, but quantitative flow tracking remains inadequate despite the critical importance of blood flow. This project aims to develop a novel optical coherence tomography (OCT) based method for volumetric, dynamic, and quantitative analysis of blood flow based on the hypothesis that temporal spatial analysis of pixel fluctuation in OCT images over multiple cardiac cycles can reveal quantitative measures of blood flow. In this cross disciplinary project, I will combine live mouse embryo dissection and culture, optimize a custom operation protocol for our lab’s house-built OCT system, and develop quantitative approaches for OCT image processing. This method will be applied to build the first 4D (volume + time) map of early mouse embryonic blood flow and will set a platform for functional cardiovascular phenotyping. Structural OCT imaging will be performed on cultured mouse embryos on embryonic day 8.5 (E8.5) volumetrically and heartbeats aligned based on previously established methods. The proposed flow speed analysis will be based on the duration each pixel detects a particle, particle size statistics, optical microangiography, and the periodicity of the cardiac cycle. Doppler OCT in regions of defined orientation will be used as calibration and validation. The proposed quantitative OCT angiography approach for blood flow analysis in the early mouse embryonic cardiovascular system will be applied to build the first 4D quantitative cardiac flow pattern in early embryos. Implementation of this approach in existing mouse models of congenital heart defects will provide insight into the interplay between genetic and biomechanical factors in cardiac development and disease, contributing to better diagnostics, prevention, and early treatment of human congenital heart disease. Through this fellowship, I will master unique cross-disciplinary skills ranging from mouse embryo dissection, custom-built imaging systems, quantitative approaches for OCT image processing, and cardiodynamic development analysis. I will train with experts in development, optics, computation, and cardiovascular biology to advance my scientific career at the frontier of cardiovascular biomechanics.