Positron emission tomography in interstitial lung disease

A high rate of glycolysis may reflect the inflammatory activity of interstitial lung disease (ILD). This prospective study investigated whether PET can distinguish IPF, a primarily fibrotic process, from other entities of ILD that have a marked inflammatory component.

Twenty-one patients referred for surgical lung biopsy because of diffuse ILD underwent PET at the time of the lung biopsy. PET transmission scans were obtained after injecting (18)FDG intravenously. Regions of interest (ROI) were drawn on the lung images, and the standardized uptake value (SUV) was calculated for these ROI.

Of the 21 patients studied, 14 had IPF, four had non-specific interstitial pneumonia, and the remaining three patients each had respiratory bronchiolitis-ILD, sarcoidosis and Langerhan's cell histiocytosis. There was no statistically significant difference in the SUV between IPF patients and non-IPF patients (P = 0.26), although patients with IPF tended to have higher SUV. Radiographic changes tended to be more prominent in the lung bases in patients with IPF compared with non-IPF patients; however, the median ratio of SUV measured in the upper fields to the whole lungs in IPF patients was not significantly different compared with the median ratio in non-IPF patients (P = 0.31).

PET does not allow differentiation of IPF from a non-IPF diffuse interstitial pulmonary process.