Effect of Shortening the Scan Duration on Quantitative Accuracy of [(18)F]Flortaucipir Studies

PURPOSE: Dynamic positron emission tomography (PET) protocols allow for accurate quantification of [(18)F]flortaucipir-specific binding. However, dynamic acquisitions can be challenging given the long required scan duration of 130 min. The current study assessed the effect of shorter scan protocols for [(18)F]flortaucipir on its quantitative accuracy. PROCEDURES: Two study cohorts with Alzheimer’s disease (AD) patients and healthy controls (HC) were included. All subjects underwent a 130-min dynamic [(18)F]flortaucipir PET scan consisting of two parts (0–60/80–130 min) post-injection. Arterial sampling was acquired during scanning of the first cohort only. For the second cohort, a second PET scan was acquired within 1–4 weeks of the first PET scan to assess test-retest repeatability (TRT). Three alternative time intervals were explored for the second part of the scan: 80–120, 80–110 and 80–100 min. Furthermore, the first part of the scan was also varied: 0–50, 0–40 and 0–30 min time intervals were assessed. The gap in the reference TACs was interpolated using four different interpolation methods: population-based input function 2T4k_V(B) (POP-IP_2T4k_V(B)), cubic, linear and exponential. Regional binding potential (BP(ND)) and relative tracer delivery (R(1)) values estimated using simplified reference tissue model (SRTM) and/or receptor parametric mapping (RPM). The different scan protocols were compared to the respective values estimated using the original scan acquisition. In addition, TRT of the RPM BP(ND) and R(1) values estimated using the optimal shortest scan duration was also assessed. RESULTS: RPM BP(ND) and R(1) obtained using 0–30/80–100 min scan and POP-IP_2T4k_V(B) reference region interpolation had an excellent correlation with the respective parametric values estimated using the original scan duration (r(2) > 0.95). The TRT of RPM BP(ND) and R(1) using the shortest scan duration was − 1 ± 5 % and − 1 ± 6 % respectively. CONCLUSIONS: This study demonstrated that [(18)F]flortaucipir PET scan can be acquired with sufficient quantitative accuracy using only 50 min of dual-time-window scanning time. SUPPLEMENTARY INFORMATION: The online version contains supplementary material available at 10.1007/s11307-021-01581-5.