DIMINISHED TC-99M HMPAO PULMONARY UPTAKE IN EX-SMOKERS

Normally, there is no localization of Tc-99m HMPAO in the lungs. Tc-99 m uptake in smokers' lungs has been reportedly higher than in nonsmoke rs. Thus, the lung uptake may be used as a barometer of cigarette smok ing, To assess whether there is a decrease in pulmonary uptake of Tc-9 9m HMPAO after cessation of smoking, the authors investigated the lung uptake of 31 male ex-smokers in comparison to smokers and nonsmokers. Anterior and posterior images were taken 10 minutes after intravenous injection of 20-25 mCi of Tc-99m HMPAO. Regions-of-interest over the liver and lungs in the anterior view were calculated. Duration of abst inence from smoking ranged from 5 months to 50 years, The mean lung/li ver uptake in ex-smokers was 0.489 +/- 0.019 (sem). In a previous repo rt, the mean lung/liver ratio for smokers (N = 30) was 0.805 +/- 0.040 (sem) and 0.408 +/- 0.019 (sem) for nonsmokers (N = 25). Compared wit h smokers, the lung/liver uptake ratio of ex-smokers was significantly lower (P < 7 x 10(-9)). The lung/liver uptake ratio of ex-smokers was significantly higher than that of nonsmokers (P < 0.005). The authors conclude that pulmonary Tc-99m HMPAO uptake of smokers is significant ly diminished after quitting smoking. However, the lung uptake of ex-s mokers is higher than that of nonsmokers. The uptake in the lung induc ed by smoking appears to be partially reversible after the cessation o f smoking.