Fig. 3. Standardized uptake value (SUV) data from a typical subject in the lighter experimental group. The fit parameters for the scan 1 fit are:  R (putamen:cerebellum ratio of blood flow times extraction) = 1.09, k2 (rate at which activity reenters the blood from the brain) = 0.127/min, BP (binding potential) = 6.07. The full fit parameters for scan 2 are:  R = 1.34, k2 = 0.121, BP = 7.33. The flow only curve for scan 2 was calculated by fixing the binding potential value to the scan 1 value and allowing the flow sensitive parameters to vary, resulting in  R = 1.11, k2 = 0.146/min, BP = 6.07. The calculated curve indicates that if only flow changes, the activity should wash in and wash out faster than what is actually seen. The binding potential must be increased by 21% (compared to the scan 1 value) to successfully fit the scan 2 data.