[Pulmonary kinetics of 13N-ammonia in smoking subjects--a quantitative study using dynamic PET]

To evaluate the effect of smoking on nonrespiratory function in the lung, a dynamic PET with 13NH3 in the lung was performed in 18 normal volunteers without lung disease nor congestion (9 non-smokers, 4 exsmokers, 5 smokers). After intravenous bolus injection of 13NH3, twenty serial 5.5-second scans followed by six 30-second scans were performed. Regions of interests were assigned on the ventral, lateral and dorsal part of the right lung and time-activity curves were generated through 26 images. The activity curve demonstrated a biexponential clearance from the lung with fast and slow component. The retention fraction (RF), fractional size of the slow component, was calculated, and the half-times (t 1/2) of both components were also evaluated. A significant increase of RF and prolongation of t 1/2 of slow component were observed in smokers compared to non-smokers and exsmokers. However, no significant difference of RF nor t 1/2 of both components was observed between non-smokers and exsmokers. These results suggest that long term smoking may modify the pulmonary kinetics of 13NH3, but the change is reversible after cessation of smoking for one year or longer.