208 Chapter 8 were referred to the memory clinic (n = 85) by their general physician, a neurologist, or a geriatrician and underwent an extensive standardized diagnostic workup that included a neurologic and neuropsychological examination, laboratory testing, and brain MRI. In a consensus meeting, participants were labeled SCD when cognitive performance appeared within normal limits, and criteria were not met for mild cognitive impairment (MCI), dementia, or other neurological or psychiatric diseases that could possibly cause cognitive complaints. Individuals received a diagnosis of MCI when they had cognitive impairment in one or more cognitive domains, while independence in functional abilities was still preserved [10]. Individuals were diagnosed with dementia when they had cognitive impairment in two or more cognitive domains, which interfered with daily activities [1]. In addition, seven participants were included via the Dutch Brain Research Registry (hersenonderzoek.nl). They experienced cognitive complaints in absence of objective impairment and received the same baseline work-up. At annual follow-up visits, neuropsychological testing was repeated and diagnoses were re-evaluated. PET and MRI acquisition Baseline dynamic [18F]florbetapir PET scans were acquired on a Philips Ingenuity TF PET-CT (n = 82) or a Philips Gemini TF PET-CT (n = 10; Philips, Best, the Netherlands) scanner. These scanners were calibrated to each other. The scan protocol started with a low-dose CT for attenuation correction. Dynamic PET scans of 90 min (n = 82) were obtained starting directly after tracer injection of approximately 370 MBq [18F]florbetapir. During the course of the study, we demonstrated that scan duration could be reduced without compromising the reliability of results [11]. Therefore, subsequent scans had a duration of 70 minutes (n = 9). One scan was terminated early after 79 min due to participant related issues. All underwent a follow-up [18F]florbetapir PET with a mean follow-up time of 2.5 ± 0.7 years (n = 17 90-min scan; n = 75 a 70-min scan). All scans were visually assessed as “positive” or “negative” by a trained nuclear physician, blinded to the amyloid status at the other time point. Baseline dynamic [18F]flortaucipir PET scans were acquired on a Philips Ingenuity TF PET-CT scanner (Philips, Best, the Netherlands, n = 44). Because substantial tau pathology within A− cognitively normal individuals is not expected to be present, we selected more A+ individuals for the [18F]flortaucipir PET in order to have a broader spectrum of amyloid and tau pathology, resulting in an A+ rate of this subset of about 33%. The scan protocol started with a low-dose CT for attenuation correction. Starting simultaneously with tracer injection of approximately 240 MBq [18F]flortaucipir, a 60-min dynamic emission scan was initiated. After a 20-min break and following a second low-dose CT for attenuation correction, an additional dynamic emission scan was performed during the interval 80–130 min post-injection.
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