Idiopathic Pulmonary Fibrosis and Diffuse Parenchymal Lung Disease: Implications from Initial Experience with 18F-FDG PET/CT

The purpose of this study was to evaluate integrated F-18-FDG PET/CT in patients with idiopathic pulmonary fibrosis (IPF) and diffuse parenchymal lung disease (DPLD). Methods: Thirty-six consecutive patients (31 men and 5 women; mean age +/- SD, 68.7 +/- 9.4 y) with IPF (n = 18) or other forms of DPLD (n = 18) were recruited for PET/CT and high-resolution CT (HRCT), acquired on the same instrument. The maximal pulmonary F-18-FDG metabolism was measured as a standardized uptake value (SUVmax). At this site, the predominant lung parenchyma HRCT pattern was defined for each patient: ground-glass or reticulation/honeycombing. Patients underwent a global health assessment and pulmonary function tests. Results: Raised pulmonary F-18-FDG metabolism in 36 of 36 patients was observed. The parenchymal pattern on HRCT at the site of maximal F-18-FDG metabolism was predominantly ground-glass (7/36), reticulation/honeycombing (26/36), and mixed (3/36). The mean SUVmax in patients with ground-glass and mixed patterns was 2.0 +/- 0.4, and in reticulation/honeycombing it was 3.0 +/- 1.0 (Mann-Whitney U test, P = 0.007). The mean SUVmax in patients with IPF was 2.9 +/- 1.1, and in other DPLD it was 2.7 +/- 0.9 (Mann-Whitney U test, P = 0.862). The mean mediastinal lymph node SUVmax (2.7 +/- 1.3) correlated with pulmonary SUVmax (r = 0.63, P < 0.001). Pulmonary F-18-FDG uptake correlated with the global health score (r = 0.50, P = 0.004), forced vital capacity (r - 0.41, P - 0.014), and transfer factor (r - 0.37, P - 0.042). Conclusion: Increased pulmonary F-18-FDG metabolism in all patients with IPF and other forms of DPLD was observed. Pulmonary F-18-FDG uptake predicts measurements of health and lung physiology in these patients. F-18-FDG metabolism was higher when the site of maximal uptake corresponded to areas of reticulation/honeycomb on HRCT than to those with ground-glass patterns.