Comparison of static 18F-FDG-PET/CT (SUV, SUR) and dynamic 18F-FDG-PET/CT (Ki) for quantification of pulmonary inflammation in acute lung injury
Journal of Nuclear Medicine
PET imaging with 18 F-FDG followed by mathematic modeling of the pulmonary uptake rate (K i ) is the gold standard for assessment of pulmonary inflammation in experimental studies of acute respiratory distress syndrome (ARDS). However, dynamic PET requires long imaging and allows the assessment of only 1 cranio-caudal field of view (∼15 cm). We investigated whether static 18 F-FDG PET/CT and analysis of SUV or standardized uptake ratios (SUR stat , uptake time-corrected ratio of 18 F-FDG
... of 18 F-FDG concentration in lung tissue and blood plasma) might be an alternative to dynamic 18 F-FDG PET/ CT and Patlak analysis for quantification of pulmonary inflammation in experimental ARDS. Methods: ARDS was induced by saline lung lavage followed by injurious mechanical ventilation in 14 anesthetized pigs (29.5-40.0 kg). PET/CT imaging sequences were acquired before and after 24 h of mechanical ventilation. K i and the apparent volume of distribution were calculated from dynamic 18 F-FDG PET/ CT scans using the Patlak analysis. Static 18 F-FDG PET/CT scans were obtained immediately after dynamic PET/CT and used for calculations of SUV and SUR stat . Mean K i values of the whole imaged field of view and of 5 ventro-dorsal lung regions were compared with corresponding SUV and SUR stat values, respectively, by means of linear regression and concordance analysis. The variability of the 18 F-FDG concentration in blood plasma (arterial input function) was analyzed. Results: Both for the whole imaged field of view and ventro-dorsal subregions, K i was linearly correlated with SUR stat (r 2 $ 0.84), whereas K i -SUV correlations were worse (r 2 # 0.75). The arterial input function exhibited an essentially invariant shape across all animals and time points and can be described by an inverse power law. Compared with K i , SUR stat and SUV tracked the same direction of change in regional lung inflammation in 98.6% and 84.3% of measurements, respectively. Conclusion: The K i -SUR stat correlations were considerably stronger than the K i -SUV correlations. The good K i -SUR stat correlations suggest that static 18 F-FDG PET/CT and SUR stat analysis provides an alternative to dynamic 18 F-FDG PET/CT and Patlak analysis, allowing the assessment of inflammation of whole lungs, repeated measurements within the period of 18 F-FDG decay, and faster data acquisition.