Abstract
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Objectives Amyloid imaging with fluorine-18 labelled radiotracers will allow widespread use of this technique, facilitating research, diagnosis and therapeutic development for Alzheimer’s disease (AD). The purpose of this study was to compare the recently developed amyloid radiotracer, 18F-AZD4694 (AZD), to 11C-PiB (PiB) in the same subjects.
Methods Twenty-five participants underwent PET imaging with PiB (40-70 min) and AZD (0-70 min): 13 healthy elderly controls (HC, 75±8 yo, MMSE 29±1), 7 subjects with mild cognitive impairment (MCI, 76±11 yo, MMSE 27±3) and 5 patients with dementia (69±9 yo, MMSE 24±3). PiB and AZD images were co-registered so that region of interest placement was identical on both scans and standard uptake value ratios (SUVR) using the cerebellar cortex as reference region were calculated between 40-70 min post injection for both PiB and AZD.
Results In the dynamic evaluation, AZD showed reversible binding kinetics reaching apparent steady state at about 40 min after injection. Both radiotracers presented a similar dynamic range of neocortical SUVR (1.1 to 2.8 and 1.1 to 2.7 SUVR for PiB and AZD, respectively) and identical low non-specific white matter retention, with frontal cortex to white matter ratios of 0.9±0.3 for both PiB and AZD. There was an excellent linear correlation between PiB and AZD neocortical SUVR (slope of 0.95, r=0.98, p<0.0001).
Conclusions 18F-AZD4694 seems a very suitable F-18 radiotracer for imaging AD pathology in vivo, with very similar imaging characteristics to 11C-PiB.
Research Support Supported in part by AztraZeneca