Nineteen healthy tobacco smokers (9 men, 10 women; 41.1±9.0 years; 13 Caucasian, 5 African American, 1 Hispanic) and 20 age-matched healthy controls (9 men, 11 women; 42.4±9.8 years; 10 Caucasian, 7 African American, 2 Hispanic, 1 Asian) participated in this study. Smokers participated in up to four [123I]5-IA SPECT scans and one magnetic resonance imaging (MRI) study. Subjects were grouped into the following time points of abstinence: 1 day (1.0±0 days; mean ± SD, n=7), 1 week (7.7±1.4 days, n=17), 2 weeks (17.9±3.0 days, n=7), 4 weeks (30.5±4.3 days, n=11), and 6-12 weeks (69.0±23.5 days, n=6). Subjects were grouped as described due to the difficulty in retaining subjects who remained abstinent over long periods and due to the challenges in having subjects complete time consuming (e.g., >8 h day) scans on multiple days. Subjects were scanned during a range of days at each time point due to scheduling constraints. Nonsmoker controls (n=20) participated in one [123I]5-IA SPECT scan and one MRI study.
