Objective: In-vivo imaging of beta-amyloid plaques (Abeta) may improve both early detection of Alzheimer disease (AD) and efficacy assessment of new treatments for AD. The authors' aim was to develop a novel Abeta-specific positron-emission tomography (PET) tracer.
Methods: Five female AD patients (54-77 years old) and six healthy female comparison subjects (53-74 years old), completed 2-hour PET scans after intravenous injection of 10 mCi of both the stilbene [11C]SB-13 and the benzothiazole [11C]6-OH-BTA-1 (also known as [11C]PIB). Kinetic analyses were performed on the resulting time-activity curves to derive Abeta binding-potential estimates, using as input function either the unmetabolized tracer concentration in venous plasma from a two-tissue compartment model or the density of radioactivity in the cerebellum. Authors compared the binding characteristics of the two radiotracers.
Results: The two radiotracers demonstrated similar binding properties with respect to regional distribution of retention (increased retention in the frontal and posterior temporal-inferior parietal association cortices in the AD patients, but not in the comparison subjects). Our preliminary PET data indicate that [11C]SB-13 may be similar to [11C]PIB in discriminating AD patients from comparison subjects.
Conclusions: [11C]SB-13 is an effective PET tracer for fibrillar Abeta imaging in vivo, with similar performance as [11C]PIB. Future research directions include evaluation of tracer in larger AD patient samples and in subjects with amnestic mild cognitive impairment, evaluation of arterial input function, and comparison with other tracers, such as [18F]FDG as they relate to cognitive functioning.