Optimized Contrast-Enhanced Micro-Computed Tomography for Simultaneous Imaging of the Ductus Arteriosus and Pulmonary...

Contrast-enhanced micro-computed tomography (micro-CT) provides high-resolution, three-dimensional visualization of small vascular structures in situ, enabling detailed analysis of morphological changes in the perinatal vasculature. The ductus arteriosus (DA) connects the aorta and pulmonary artery (PA), diverting placentally oxygenated blood away from the lungs in utero. Both DA and PA undergo rapid changes in tone with the first breath during the transition from fetal to neonatal oxygen conditions. This study aimed to optimize contrast-enhanced micro-CT protocols to enable simultaneous visualization of the DA and pulmonary vasculature during this transition in fetal rabbits. Two contrast agents, an iodine-based agent (Omnipaque, 300 mg/mL) and two forms of a barium sulphate suspension, were compared to determine which optimally opacified the DA and pulmonary circulation in fetal rabbit kits (n = 22) from new-term New Zealand white rabbits (n = 4). Micro-CT imaging was performed to assess DA patency and changes in PA caliber across a wide range of vessel diameters from ~50 µm to > 1 mm under hypoxia versus normoxia in anesthetized kits. Omnipaque provided adequate opacification of the DA but limited visualization of the pulmonary vasculature. However, unfiltered 25% barium sulfate in 3% gelatin achieved robust, simultaneous visualization of the DA and pulmonary circulation. This agent optimally enhanced contrast in both large vessels and small PAs, enabling simultaneous assessment of DA constriction and pulmonary arterial vasodilation within 20 min of breathing oxygen. This study established an optimal contrast agent and micro-CT imaging strategy for post-mortem assessment of DA and pulmonary vascular morphology during the perinatal transition.