Amyloid plaque imaging from IMPY/SPECT to AV-45/PET.

The formation and deposition of β-amyloid (Aβ) plaques are the earliest pathological changes in Alzheimer's disease (AD). Molecular imaging of Aβ plaques could serve as a surrogate marker in early diagnosis and neuropathogenesis studies of AD. Several radionuclide labeled ligands have recently been developed for noninvasive visualization of Aβ plaques in the brains of AD patients using single photon emission computed tomography or positron emission tomography (PET). There has been rapid progress in the field of imaging for plaque pathology. AV-45 was the first plaque imaging agent to enter multi-center, investigational new drug clinical trials in the US, and has now been studied in dozens of trials with more than 1,000 subjects ranging from cognitively normal individuals to those with AD dementia. "Imaging to autopsy" phase III studies further confirmed and validated the specific imaging signal correlated to the plaque burden in living subjects. With these promising and confirmed characteristics of AV-45, the Alzheimer's Disease Neuroimaging Initiative (ADNI) under common consensus decided on AV-45 as the emerging standard PET imaging agent for evaluating the progression of plaque pathology in patients with AD or mild cognition impairment, and even healthy controls. With the wide availability of AV-45 for plaque imaging, the ultimate goal of the ADNI is global clinical trials for disease detection and progression. This review presents recent experience with Aβ-targeting radiotracers at Chang Gung University and Chang Gung Memorial Hospital.