Perfusion-Phase ¹⁸ F-PI-2620 Tau-PET Imaging as a Surrogate Marker of Neuronal Injury

Ziel/Aim Second generation tau radioligands for use with positron emission tomography (PET) have been developed for visualization of tau deposits in vivo.For several β-amyloid and first generation tau radioligands, it has been shown that reduced early-phase perfusion can be used as a surrogate of neuronal injury. Therefore, we investigated the performance of early acquisitions of the novel tau radioligand¹⁸F-PI-2620 for the assessment of neuronal injury.

Methodik/Methods Twenty-six subjects were referred with suspected tauopathies and received a dynamic ¹⁸F-PI-2620 tau-PET (0-60 min p.i.) and ¹⁸F-fluorodeoxyglucose (FDG)-PET (30-50 min p.i.). Regional standard-uptake-value-ratios of early-phase perfusion images (single frame SUVr) and the blood flow estimate (R₁) of ¹⁸F-PI-2620 were correlated with corresponding quantification of FDG-PET (global mean/cerebellar normalisation). Reduced tracer uptake in cortical target regions was also interpreted visually using 3-dimensional stereotactic surface projections by three experienced and three expert readers and intraclass correlation coefficients (ICC) were calculated between tau-PET perfusion and FDG-PET.

Ergebnisse/Results Highest agreement with FDG quantification was reached for ¹⁸F-PI-2620 acquisition from 0.5 to 2.5 min p.i. for global mean (R > 0.69) and cerebellar scaling (R > 0.63). Correlation coefficients (summed 0.5-2.5 min SUVr & R₁) displayed excellent agreement in all cortical target regions for global mean (R_SUVr0.75 ± 0.10, R_R1= 0.75 ± 0.10) and cerebellar normalization (R_SUVr0.67 ± 0.10, R_R1= 0.67 ± 0.12). Visual interpretation revealed high regional ICC between tau-PET perfusion and FDG-PET independent of the reader experience (ICC_SUVr= 0.62 ± 0.07, ICC_R1= 0.66 ± 0.07).

Schlussfolgerungen/Conclusions Perfusion phase imaging of ¹⁸F-PI-2620 can serve as a surrogate biomarker for neuronal injury. Dynamic imaging or a dual time point protocol for tau-PET imaging could replace additional FDG-PET imaging by indexing both the distribution of tau and the amount of neuronal injury.