ORIGINAL ARTICLE Areas of normal pulmonary parenchyma on HRCT exhibit

Purpose Patients with idiopathic pulmonary fibrosis (IPF) show increased PET signal at sites of morphological abnor-mality on high-resolution computed tomography (HRCT). The purpose of this investigation was to investigate the PET signal at sites of normal-appearing lung on HRCT in IPF. Methods Consecutive IPF patients (22 men, 3 women) were prospectively recruited. The patients underwent 18F-FDG PET/HRCT. The pulmonary imaging findings in the IPF patients were compared to the findings in a control population. Pulmonary uptake of 18F-FDG (mean SUV) was quantified at sites of morphologically normal parenchyma onHRCT. SUVs were also corrected for tissue fraction (TF). The mean SUV in IPF patients was compared with that in 25 controls (patients with lymphoma in remission or suspected paraneoplastic syndrome with normal PET/CT appearances). Results The pulmonary SUV (mean±SD) uncorrected for TF in the controls was 0.48±0.14 and 0.78±0.24 taken from normal lung regions in IPF patients (p<0.001). The TF-corrected mean SUV in the controls was 2.24±0.29 and 3.24±0.84 in IPF patients (p<0.001). Conclusion IPF patients have increased pulmonary uptake of 18F-FDG on PET in areas of lung with a normal morpho-logical appearance on HRCT. This may have implications for determining disease mechanisms and treatment monitoring