Lung uptake of Tc-99m HMPAO in cigarette smokers expressed by lung/liver activity ratio

Tc-99m HMPAO, a lipophilic radiopharmaceutical used for brain imaging, has been reported to localize in smokers' lungs. To quantitate this uptake in the lung, 55 patients, who were referred for brain imaging for dementias or strokes, also underwent lung imaging (anterior lung imaging includes a large part of the liver) after IV injection of the radiopharmaceutical. Regions of interest over the liver and the lung were calculated. Of the 55 patients (ages 13-79), 30 were smokers and 25 were nonsmokers. The smokers had been smoking from 6-59 years, and daily cigarette consumption ranged from 8-50 cigarettes. The mean lung/liver ratio for smoking patients were 0.792 +/- 0.042 (SE); the mean lung/liver ratio for nonsmoking patients was 0.408 +/- 0.019 (SE). Lung/liver ratio uptake was significantly higher in the smoking patients (P < 0.01) than in the nonsmokers. Thus, lung/liver uptake of Tc-99m HMPAO may be used as an indicator of cigarette smoking.