Imaging allergen-invoked airway inflammation in atopic asthma with [18F]-fluorodeoxyglucose and positron emission tomography

Background Airway inflammation is a feature of asthma and can be quantified invasively with bronchial lavage and endobronchial histology. Inflammatory foci can be imaged non-invasively with positron emission tomography (PET) and [18F]-fluorodeoxyglucose (18FDG) to quantify glucose uptake in activated granulocytes. We used this technique to study airway inflammation in asthma. Methods Nine men with mild atopic asthma were studied. In five, we studied the effect of bronchoscopic segmental allergen challenge on 18FDG uptake. Allergen was instilled into the posterior segment of the right upper lobe; a similar volume (20 mL) of isotonic saline was instilled into the posterior segment of the left upper lobe. At 1-32 h after instillation, PET with 18FDG was done. In the other four patients, we administered aerosolised allergen. Findings 18FDG uptake was increased four-fold in the right compared with the left upper lobe (geometric mean of ratios 4·30, 95% Cl 2·39-7·72, P=0·002). Aerosolised administration of allergen did not significantly increase 18FDG uptake. Interpretation These data show that local allergen-invoked airway inflammation can be visualised with 18FDG and PET in asthma. The cellular localisation of the 18FDG signal remains to be determined.