Noninvasive quantitative assessment of pulmonary blood flow with 11F-FDG PET

Abstract

Pulmonary blood flow (PBF) is a critical determinant of oxygenation during acute lung injury (ALI). PET/CT with 11F-FDG allows the assessment of both lung aeration and neutrophil inflammation as well as an estimation of the regional fraction of blood (FB) if compartmental modeling is used to quantify 11F-FDG pulmonary uptake. The aim of this study was to validate the use of FB to assess PBF, with PET and compartmental modeling of 15O-H2O kinetics as a reference method, in both control animals and animals with ALI. For the purpose of studying a wide range of PBF values, supine and prone positions and various positive end-expiratory pressures (PEEPs) and tidal volumes (VTs) were selected. Methods: Pigs were randomized into 3 groups in which ALI was induced by HCl inhalation: pigs studied in the supine position with a low PEEP (5 ± 3 [mean ± SD] cm of H2O; n = 9) or a high PEEP (12 ± 1 cm of H2O; n = 8) and pigs studied in the prone position with a low PEEP (6 ± 3 cm of H2O; n = 9). Also included were a control group that did not have ALI (n = 6) and 2 additional groups (n = 6 each) that had a high VT to maintain a transpulmonary pressure of greater than or equal to 35 cm of H2O and that either received HCl inhalation or did not receive HCl inhalation. PBF and FB were measured with PET and compartmental modeling of 15O- H2O and 11F-FDG kinetics in 10 lung regions along the anterior-to-posterior lung dimension, and both were expressed in each region as a fraction of their values in the whole lung. Results: PBF and FB were strongly correlated (R2 = 0.9), with a slope of the regression line close to unity and a negligible intercept. The mean difference between PBF and FB was 0, and the 95% limits of agreement were -0.035 to 0.035. This good agreement between methods was obtained in both normal and injured lungs and under a wide range of VT, PEEP, and regional PBF values (7-71 mL/kg, 0-15 cm of H2O, and 24-603 mL· min-1·100 mL of Lung-1, respectively). Conclusion: FB assessed with 11F-FDG is a good surrogate for PBF in both normal animals and animals with ALI. PET/CT has the potential to be used to study ventilation, perfusion, and lung inflammation with a single tracer. COPYRIGHT © 2013 by the Society of Nuclear Medicine and Molecular Imaging, Inc.