Potential of 18F-FDG-PET in the Global Assessment of Lung Inflammation

2012 Objectives: Review the present use of 18F-FDG-PET in lung inflammation/interstitial lung diseases. Review the potential value of 18F-FDG-PET in the global measurement and monitoring of lung inflammation/interstitial lung diseases. Assess the added prospective value of 18F-FDG-PET imaging in inflammatory diseases involving the lung. Methods: In light of the ongoing SARS-COV-2 pandemic, more attention has been drawn to lung disorders. Medical imaging can play a major role in disease assessment here, given that early diagnosis of various lung disorders is crucial. Regarding such diseases, increased glucose uptake in lung parenchyma is a hallmark of several pathophysiological processes, including inflammation and development of benign/malignant tumors. Major risk factors for such increased glucose uptake include smoking, environmental irritants, viral infections etc. Numerous studies have directly shown that global 18F-fluorodeoxyglucose-positron emission tomography (18F-FDG-PET) is one of the most sensitive modalities to measure glucose uptake, albeit in other areas of the body like the heart and liver. 18F-FDG-PET is especially effective in early stage measurement, given its inherent property as a method to assess increased metabolic activity in inflammation occurring long before structural changes. As of yet though, little original research exists in the current literature specifically regarding the utility of 18F-FDG-PET for the assessment of inflammation in the human lung. We believe that this is an area of high interest, given the reasons listed above and the increased emphasis on earlier diagnosis of common lung disorders (thus necessitating the prioritization of molecular as compared to structural imaging). Results: Numerous research by our own lab and fellow colleagues has found that 18F-FDG-PET can successfully quantify tumor growth for various forms of lung cancer, in both human and animal models. Despite this, as mentioned above, no such definitive conclusion can be made about human lung inflammation. The current state of the field centers mainly around studying in vivo application of 18F-FDG-PET to animal models, which has been successfully done in both sheep and rat lungs. We believed that this application could extend to the human body, and thus hypothesized that quantifying human lung inflammation through 18F-FDG-PET would show similar promise. And indeed, our retrospective research (currently in submission) has found that inflammation of the lung, as globally assessed by 18F-FDG-PET, is significantly higher in smokers compared to nonsmokers, while also being positively correlated with age. Global assessment of the lung here was key, in order to represent the true extent of inflammation across the entire lung rather than cherry-picking isolated focal nodules. Conclusions: 18F-FDG-PET can likely play a valuable role in management of lung disorders, especially in novel areas such as lung inflammation. However, the lack of original, prospective data on human models necessitates further research. Specifically, well-powered studies should be conducted to explore in vivo 18F-FDG-PET uptake in lung parenchyma and to compare 18F-FDG-PET sensitivity/specificity with other imaging modalities in the lung.