Improving Pulmonary Perfusion Assessment by Dynamic Contrast-Enhanced Computed Tomography in an Experimental Lung Injury Model.

Pulmonary perfusion has been poorly characterized in acute respiratory distress syndrome(ARDS). Optimizing protocols to measure pulmonary blood flow() via dynamic contrast-enhanced(DCE) computed tomography(CT) could improve understanding of how ARDS alters pulmonary perfusion. In this study, comparative evaluations of injection protocols and tracer-kinetic analysis models were performed based on DCE-CT data measured in ventilated pigs with and without lung injury. 10 Yorkshire pigs were anesthetized, intubated, and mechanically ventilated; lung injury was induced by bronchial hydrochloric acid instillation. Each DCE-CT scan was obtained during 30-second end-expiratory breath-hold. Reproducibility of measurements was evaluated in 3 pigs. In 8 pigs, undiluted and diluted Isovue-370 were separately injected to evaluate the effect of contrast viscosity on estimated values. was estimated with the peak-enhancement and the steepest-slope approach. Total-lung was estimated in 2 healthy pigs to compare with cardiac output measured invasively by thermodilution in the pulmonary artery. Repeated measurements in the same animals yielded a good reproducibility of computed maps. Injecting diluted isovue-370 resulted in smaller contrast-time curves in the pulmonary artery(<0.01) and vein(<0.01) without substantially diminishing peak signal intensity(=0.46 in the pulmonary artery) compared to the pure contrast agent since its viscosity is closer to that of blood. As compared to the peak-enhancement model, values estimated by the steepest-slope model with diluted contrast were much closer to the cardiac output(=0.82) as compared to the peak-enhancement model. DCE-CT using the steepest-slope model and diluted contrast agent provided reliable quantitative estimates of .