Cystic fibrosis: Detecting changes in airway inflammation with FDG PET/CT

Purpose: To determine if fluorine 18 fluorodeoxyglucose (FDG) positron emission tomographic (PET)/computed tomographic (CT) imaging can depict a treatment effect from intravenous antibiotics for pulmonary exacerbation in cystic fibrosis (CF). Materials and Methods: The study was approved by the institutional review board of the Hospital for Sick Children and by Health Canada. Consent was obtained from all subjects. Patients with CF who were between 6 and 18 years of age and were admitted for a pulmonary exacerbation were eligible for the study. FDG PET/CT examinations (with low-dose CT) were performed on days 1 and 14 of admission (±72 hours). PET activity was quantified by using standardized uptake values (SUVs) through assessment of background activity (mean SUV [SUVmean]) and superimposed focal uptake (maximum SUV [SUVmax]) for each lung zone. CT studies were scored by using the CF-CT model. SUVs from pre- and posttherapy studies were compared by using paired t tests. Unpaired t tests were used to compare data in patients with CF and data in 10 control subjects. Results: Twenty patients with CF were enrolled. Antibiotic therapy resulted in a significant decrease in SUVmax (mean difference, 2.3 ± 2.1 [standard deviation], P < .0001). Pretherapy SUVmax and SUVmean and posttherapy SUVmax were significantly different from those in control subjects. The change in SUVmax and percentage predicted forced expiratory volume in 1 second was negatively correlated. (R = 20.72, P = .004). Overall CF-CT scores significantly correlated with SUVmax (R = 0.40, P = .01). Conclusion: FDG PET/CT is a useful tool for detecting inflammatory changes resulting from treatment for pulmonary exacerbations in pediatric patients with CF. Inflammatory changes detected by using FDG PET/CT correlated with lung function, sputum neutrophil counts, and CF-CT scores. Analyzing focal lung inflammation (with SUVmax) may be a feasible way to measure airway inflammation in patients with CF.

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