Regional pulmonary perfusion using model-free analysis of contrast-enhanced MRI in meconium-aspirated piglets

PURPOSE: To investigate if dynamic contrast-enhanced MRI in lungs could add new information to pulmonary hypertension in a newborn piglet model. MATERIALS AND METHODS: Six newborn piglets were subjected to instillation of meconium following treatment with sildenafil. Before and after both of these events, dynamic contrast-enhanced MRI was performed to determine pulmonary blood flow (PBF) using a model-free deconvolution of the dynamic signal-time curve, together with invasive measurements of mean airway pressure (PAW), cardiac output (CO), and oxygenation index (OI). RESULTS: Meconium instillation caused a significant increase in PAW (P < 0.05) accompanied by a marked increase in OI, the average PBF in the four lung regions (apical-anterior, apical-posterior, distal-anterior, and distal-posterior) decreased significantly by 33% (P < 0.001), but it did not significantly affect CO. On the other hand, infusion of sildenafil caused a significant increase in CO (P < 0.01), and administration resulted mainly in an increased PBF in the distal parts of the lungs. CONCLUSION: By using dynamic contrast-enhanced MRI, we demonstrated a marked decrease in PBF following instillation of meconium, which was not followed by an equivalent decrease in CO, suggesting that measurements of CO inadequately reflect the intrapulmonary changes in the blood circulation.