Dynamic in vivo PET imaging was carried out in WT mice (n = 8) in order to assess the tracer distribution and brain uptake for [ 18 F]12 (Figure ). An initial peak of activity and subsequent rapid washout in blood and lungs was observed after tracer injection. The activity then predominantly accumulated in the liver, kidneys, bladder and intestines (Figure ). Elevated bone uptake indicating radio-defluorination in vivo, was not detected. The brain time-activity-curve (TAC) demonstrated that [ 18 F]12 successfully crossed the BBB with a maximum brain uptake CMax of 2.5 ± 0.7 SUV within the first two minutes p.i., followed by a rapid tracer clearance (Figure ). 25 minutes after tracer administration, the activity signal reached a plateau phase with a slow decrease in signal intensity (C25min/C60min ~ 1.5). Mouse organs were collected 60 min p.i. after intracardial perfusion to quantify the tracer uptake ex vivo. [ 18 F]12 still exhibits an activity level of 0.6 ± 0.2 %ID/g in the brain, demonstrating that a substantial amount of tracer remained in the CNS after the PET scan (Figure , Table ).