Imaging Alzheimer's disease pathology: one target, many ligands

Over the past five years there has been a surge of interest in using positron emission tomography (PET) to determine the in vivo density of the senile plaque, a key pathological feature of Alzheimer's disease. The development of the tracers [11C]-PIB, [11C]-SB13 and [18F]-FDDNP has coincided with drug strategies aimed at altering the brain metabolism of amyloid-β peptides. The evolution of these novel ligands serves not only as an excellent example of how rapidly imaging technologies can progress but also as a reminder that the fundamental biological knowledge, which is necessary to fully interpret the PET data, can be left trailing behind.