26 Chapter 2 tracer kinetic modelling. Therefore, the aim of the study is to investigate whether a shorter overall scan duration for [18F]flortaucipir PET dual-time- window scans is feasible, while retaining quantitative accuracy. METHODS Study Sample For the current project, two study cohorts were included. The first cohort consisted of ten biomarker (PET/CSF)-confirmed AD patients and ten cognitively normal controls who underwent a 130-min dynamic [18F]flortaucipir PET scan with arterial sampling (“full kinetic model cohort”). Subject characteristics have been described previously [18]. The second cohort consisted of eight subjects with AD and six cognitively normal controls that underwent two 130-min dynamic [18F]flortaucipir PET scans within a time interval of minimum 1 week, and maximum 4 weeks (“test-retest cohort”). The subject characteristics have been described previously [19]. The current study was approved by the Medical Ethics Committee of the Amsterdam University Medical Center. All subjects signed an informed consent form prior to participation. Scan Procedures T1-weighted MRI scans were acquired for all participants using a 3.0 T Philips Ingenuity Time-of-Flight PET/MR scanner (Philips medical systems, Best, the Netherlands). Isotropic structural 3D T1-weighted images were obtained using a sagittal turbo field echo sequence (1.00 mm3 isotropic voxels, repetition time = 7.9 ms, echo time = 4.5 ms, flip angle = 8°) for brain tissue segmentation. All subjects from the full kinetic model cohort underwent a 130-min dynamic [18F]flortaucipir PET scan on a Gemini TF-64 PET/CT scanner (Philips Medical Systems, Best, The Netherlands) with continuous arterial sampling after administration of 223 ± 18 MBq of [18F]flortaucipir. Details described elsewhere [17–19]. Subjects from the test-retest cohort underwent two 130-min dynamic [18F]flortaucipir PET scans on a Philips Ingenuity TF PET/CT scanner after administration of [18F]flortaucipir (237 ± 15 MBq at test and 245 ± 18 MBq at retest) as described in detail previously [19]. In short, a low-dose CT for attenuation correction was acquired, followed by a 60-min dynamic (brain) emission scan initiated simultaneously with tracer injection. After a 20-min break, a second low-dose CT was acquired before an additional dynamic emission scan during the interval 80–130 min p.i. During scanning, the head of the subjects was stabilized to reduce movement artefacts. Furthermore, subjects were positioned within the center of axial and transaxial fields of view, such that the orbitomeatal line was parallel to the detectors with the use of laser beams.
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