Objectives The accumulation of tau in the basal ganglia and later cerebellum and frontal cortex is a key pathogenic mechanism in Progressive Supranuclear Palsy (PSP). The ability to detect tau in the living brain has the potential to revolutionise the diagnosis of PSP and other tauopathies, and to monitor the effectiveness of therapeutic interventions targeting tau-based mechanisms. This study investigates the use of a new tau-specific PET radiotracer, PI-2620, as a tool for visualising tau in the living brain.

Methods Ten patients with PSP (age 62-75 years, 6 male) underwent a 60 minute dynamic PET scan with PI2620 (185MBq). The dynamic PET data was processed in to a single parametric image of binding potential (BP) using the simplified reference tissue model and the corpus callosum as the reference region.

Results Visual inspection of the images showed clear uptake in the basal ganglia nuclei. BP was highest in pallidum (1.99), putamen (1.67), thalamus (1.63), substantia nigra (1.62), cerebellum (1.6) and caudate (1.55), compared to 1.2-1.5 across the cortical regions. Higher BP in the basal ganglia nuclei were associated with higher scores on the PSPRS (putamen, r=0.77, p=0.01).

Conclusion PI2620-PET shows promising potential as a technique for specifically imaging and quantitating the topographic pattern of tau distribution in patients with PSP. Further studies are needed to evaluate its use as a diagnostic and treatment monitoring tool for PSP and other tauopathies.