Tc-99m HMPAO diffuse pulmonary uptake demonstrated in cigarette smokers.

Tc-99m HMPAO, a lipophilic radiotracer used as a brain SPECT imaging agent in the diagnosis of strokes and dementias, is normally localized in the brain and the heart and is excreted through the kidneys (50%) and the hepatobiliary system (14% to 30%). There is no pulmonary localization except in the lungs of smokers. To evaluate pulmonary localization of Tc-99m HMPAO in relation to smoking, 23 patients (aged 27 to 76 years) who were referred for brain imaging studies for strokes or dementias also underwent lung imaging studies immediately following the brain imaging. Anterior and/or posterior lung images were obtained 30 to 45 minutes after IV injection of 15 mCi Tc-99m HMPAO. Diffuse pulmonary uptake was graded semiquantitatively: 3+, pulmonary uptake is equal to or higher than hepatic uptake; 2+, pulmonary uptake is less than hepatic uptake but higher than cardiac uptake; 1+, pulmonary uptake is equal to cardiac uptake; 0, pulmonary uptake is less than cardiac uptake. Each patient's smoking history, including duration and daily consumption, was recorded. Four patients' lung images showed 3+ lung uptake; 6 patients, 2+; 1 patient, 1+; and 12 patients, 0 uptake. Eleven patients with lung uptakes of 3+ to 1+ had a history of cigarette smoking. Twelve patients with lung uptake less than cardiac uptake had no smoking history. Pulmonary distribution of Tc-99m HMPAO is usually negligible in the normal lung. Our results indicate that lung uptake correlates significantly (chi-square = 23, d.f. = 1, P = 0.0001) with smoking history.