A novel partial volume correction method for accurate quantification of [¹⁸F] flortaucipir in the hippocampus

Off-target binding in the choroid plexus (CP) may cause spill-in of the tau PET tracer [¹⁸F] flortaucipir into the adjacent hippocampus region. The impact of this spill-in on hippocampal uptake was assessed using a novel partial volume correction method (PVC).

PVC was performed on 20 [¹⁸F] flortaucipir dynamic PET scans (10 probable AD and 10 controls). Volumes of interest (VOIs) were defined for both hippocampus and CP. The correlation between hippocampal and CP distribution volume (V_T), with and without PVC, was determined. Both anatomically defined and eroded VOIs were used.

For controls, the correlation between hippocampal and CP V_T was significantly reduced after using PVC along with an eroded VOI (r² = 0.59, slope = 0.80 versus r² = 0.15, slope = 0.15; difference: p < 0.05). The same was true for AD patients (p < 0.05).

PVC together with an optimized hippocampal VOI resulted in effective reduction of CP spill-in and improved accuracy of hippocampal V_T.