Abstract
1891
Objectives FDG-PET has proven to be a useful tool in diagnosis, staging and prognostication of malignancies. Delayed time point imaging has also been validated in increasing the accuracy of detection of lung lesions. Recently, it has been shown that FDG PET is able to assess inflammation in various settings. In this study, we have investigated the ability of FDG-PET/CT to predict the respiratory function of a group of patients with suspected lung cancer, which might be in connection with inflammation.
Methods We investigated 16 heavy smokers with suspected lung cancer and emphysema in the lungs based on detection of emphysema by an in-house software analyzing CT scans of the patients and providing the air/tissue ratio. Each patient was scanned 1, 2 and 3 hours after injection with FDG-PET/CT. SUVmean of the lung was calculated by drawing ROIs around lung parenchyma in each slice. We correlated these parameters from each time point with quantitative pulmonary function assessment (FEV1/FVC). In order to avoid leakage from suspected tumor uptake, only the lung contralateral to the tumor was analyzed. In addition, we multiplied the FDG uptake in the lung to the ratio of air/tissue in order to correct for partial volume effect.
Results We found that averaged uptake for all patients decreased with time. The uncorrected SUVmean was 0.37 (95%CI 0.31 to 0.42), 0.33 (95%CI 0.28 to 0.38), 0.31 (95%CI 0.26 to 0.35) at 1, 2, and 3 hours, respectively. The corrected SUVmean was 0.4 (95%CI 0.314 to 0.425), 0.36 (95%CI 0.31 to 0.4), 0.33 (95%CI 0.29 to 0.38), respectively. This most likely is related to reduction of blood pool activity. This idea was further confirmed with the increased correlation between FDG uptake and pulmonary function testing over time. The first hour correlation coefficient was 0.49 (P=0.071, 95%CI -0.05 to 0.8), at second hour it was 0.52 (P=0.054, 95%CI 0 to 0.8) and at third hour, which was the only time point with statistically significant correlation, was 0.54 (P=0.043, 95%CI 0 to 0.8) for uncorrected images. The amount of FDG uptake increased after correction for partial volume in all three time points with statistical significance (P<0.05).
Conclusions The results of this study shows that FDG PET/CT might be feasible in assessment of respiratory function. This study also highlights the importance of delayed time point imaging and partial volume correction in enhancing the quality FDG PET/CT images of lung. Further studies are needed to elucidate this topic with more details.