All subjects received a 0.6-g saturated solution of potassium iodide, to protect their thyroid from possible exposure to radioactive iodide, in the hour prior to radiotracer administration. [123I]5-IA was synthesized as previously described 51 and administered as a bolus to constant infusion at a ratio of 7.0 for 8 hours. Subjects were injected with equivalent doses of a bolus (mean±SD, MBq) and constant infusion (mean±SD, MBq/h) as follows: control nonsmokers (157.9±14.6 MBq, 22.8±2.1 MBq/h), 1 day abstinent smokers (134.5±24.6 MBq, 20.5±3.8 MBq/h), 1 week abstinent smokers (154.3±15.9 MBq, 22.2±2.6 MBq/h), 2 week abstinent smokers (159.4±5.6 MBq, 23.3±0 MBq/h), 4 week abstinent smokers (158.9±7.4 MBq, 22.6±1.7 MBq/h) and 6-12 week abstinent smokers (141.5±30.5 MBq, 21.9±3.5 MBq/h). Three consecutive 30-min emission scans and one 15-min simultaneous transmission and emission protocol scan (STEP) were obtained between hours 6 and 8 of the [123I]5-IA infusion on a Picker PRISM 3000 XP (Cleveland, OH) SPECT camera. The PRISM 3000 XP is a 3-headed camera equipped with a low energy, ultra-high resolution fanbeam collimator (photopeak window, 159 keV ± 10%; matrix 128×128) with a uniform sensitivity
