PT  - JOURNAL ARTICLE
AU  - Denise Visser
AU  - Hayel Tuncel
AU  - Rik Ossenkoppele
AU  - Maqsood Yaqub
AU  - Emma E. Wolters
AU  - Tessa Timmers
AU  - Emma Weltings
AU  - Emma M. Coomans
AU  - Marijke E. den Hollander
AU  - Wiesje M. van der Flier
AU  - Bart N.M. van Berckel
AU  - Sandeep S.V. Golla
TI  - Longitudinal Tau PET Using <sup>18</sup>F-Flortaucipir: The Effect of Relative Cerebral Blood Flow on Quantitative and Semiquantitative Parameters
AID  - 10.2967/jnumed.122.263926
DP  - 2023 Feb 01
TA  - Journal of Nuclear Medicine
PG  - 281--286
VI  - 64
IP  - 2
4099  - http://jnm.snmjournals.org/content/64/2/281.short
4100  - http://jnm.snmjournals.org/content/64/2/281.full
SO  - J Nucl Med2023 Feb 01; 64
AB  - Semiquantitative PET measures such as SUV ratio (SUVr) have several advantages over quantitative measures, such as practical applicability and relative computational simplicity. However, SUVr may potentially be affected by changes in blood flow, whereas quantitative measures such as nondisplaceable binding potential (BPND) are not. For 18F-flortaucipir PET, the sensitivity of SUVr for changes in blood flow is currently unknown. Therefore, we compared semiquantitative (SUVr) and quantitative (BPND) parameters of longitudinal 18F-flortaucipir PET scans and assessed their vulnerability to changes in blood flow. Methods: Subjects with subjective cognitive decline (n = 38) and Alzheimer disease patients (n = 24) underwent baseline and 2-y follow-up dynamic 18F-flortaucipir PET scans. BPND and relative tracer delivery were estimated using receptor parametric mapping, and SUVr at 80–100 min was calculated. Regional SUVrs were compared with corresponding distribution volume ratio (BPND + 1) using paired t tests. Additionally, simulations were performed to model effects of larger flow changes in different binding categories. Results: Results in subjective cognitive decline and Alzheimer disease showed only minor differences between SUVr and BPND changes over time. Relative tracer delivery changes were small in all groups. Simulations illustrated a variable bias for SUVr depending on the amount of binding. Conclusion: SUVr provided an accurate estimate of changes in specific binding for 18F-flortaucipir over a 2-y follow-up during which changes in flow were small. Notwithstanding, simulations showed that large(r) flow changes may affect 18F-flortaucipir SUVr. Given that it is currently unknown to what order of magnitude pharmacotherapeutic interventions may induce changes in cerebral blood flow, caution may be warranted when changes in flow are potentially large(r), as in clinical trials.