Radio-labeling etc. Jellybean, it is quite clear to me (and I suspect to many other readers of this thread) that you are trying to take part in a debate with a practicing expert by using Google as your sole reference. It is clear that bobrmd works in this field and has PRACTICAL, CLINICAL experience with these radiolabeled drugs and patients. It is likewise clear that you do not have this knowledge or experience and are trying to prolong an argument simply for the sake of it.
There is a clear tendency by several apparently educated individuals on this board to believe that they know how things work because they have read a paper and think they understand the biology or physics. In medicine, like many professions, REAL WORLD experience trumps your googling. Enough already! Why not just shut up and learn something?