Inflow-weighted pulmonary perfusion: comparison between dynamic contrast-enhanced MRI versus perfusion scintigraphy in complex pulmonary circulation

Abstract

Abstract Background Due to the different properties of the contrast agents, the lung perfusion maps as measured by 99mTc-labeled macroaggregated albumin perfusion scintigraphy (PS) are not uncommonly discrepant from those measured by dynamic contrast-enhanced MRI (DCE-MRI) using indicator-dilution analysis in complex pulmonary circulation. Since PS offers the pre-capillary perfusion of the first-pass transit, we hypothesized that an inflow-weighted perfusion model of DCE-MRI could simulate the result by PS. Methods 22 patients underwent DCE-MRI at 1.5T and also PS. Relative perfusion contributed by the left lung was calculated by PS (PS L%), by DCE-MRI using conventional indicator dilution theory for pulmonary blood volume (PBV L% ) and pulmonary blood flow (PBF L% ) and using our proposed inflow-weighted pulmonary blood volume (PBV iw L% ). For PBV iw L% , the optimal upper bound of the inflow-weighted integration range was determined by correlation coefficient analysis. Results The time-to-peak of the normal lung parenchyma was the optimal upper bound in the inflow-weighted perfusion model. Using PS L% as a reference, PBV L% showed error of 49.24% to −40.37% (intraclass correlation coefficient RI = 0.55) and PBF L% had error of 34.87% to −27.76% (RI = 0.80). With the inflow-weighted model, PBV iw L% had much less error of 12.28% to −11.20% (RI = 0.98) from PS L% . Conclusions The inflow-weighted DCE-MRI provides relative perfusion maps similar to that by PS. The discrepancy between conventional indicator-dilution and inflow-weighted analysis represents a mixed-flow component in which pathological flow such as shunting or collaterals might have participated.