236 Chapter 9 markers of disease progression [25]. Furthermore, tau PET has shown to be superior to plasma markers for tau in predicting future cognitive decline in cognitively impaired individuals, which is of key interest in clinical trials [26]. Whether this also holds for cognitively unimpaired individuals is yet to be elucidated. Lastly, tau PET provides regional information about tau accumulation and thereby allows for ‘staging’ , which is currently implemented as inclusion criteria for clinical trials [27]. Harmonization of tau PET data As for solid assessment multiple studies into the role of tau PET in routine clinical workup and clinical trials are required, it is important to consider harmonization of data. Not only will studies include divers cohorts, but they might also use different tau PET tracers or processing pipelines. The amyloid PET field has greatly benefitted from the implementation of the Centiloid scale [28, 29], a scale which puts all the available PET tracers on single 100-point scale, thereby allowing a single Centiloid score across tracers to reflect the same amount of amyloid pathology [29]. Currently a similar initiative is ongoing for tau PET (CenTauRz) [30], representing a great step towards data harmonization. Concluding remarks In this thesis we demonstrated the utility of (dynamic) [18]flortaucipir PET imaging from multiple perspectives. From a methodological point of view we demonstrated that dynamic scanning protocols can be shorted without compromising on quantitative accuracy. The main benefit of dynamic acquisition is that a measure of rCBF can be obtained, as we also demonstrated that static imaging protocols are sufficient in settings (including longitudinal follow-up) where changes in flow are expected to be small. From a biological/clinical point of view this thesis highlights the potential of a single tau PET to improve the prognosis and selection of the right target population for clinical trials in the context of cortical thinning and cognition. Although several considerations remain to be solved, this thesis aided in enlarging methodological and biological insight into [18F]flortaucipir PET scans, thereby aiding its implementation and interpretability in clinical and research settings.
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