A CenTauR scale based on 18F‐MK6240

Abstract

AbstractBackgroundA standardized scale for the quantification of tau PET imaging would allow comparison and combination of data across tracers and sites resulting in large meta‐analysis and the application of universal cut‐offs. The proposed approach called CenTauR (CTR) was evaluated on 18F‐MK6240 using both global and regional anchoring.Method375 18F‐MK6240 PET & T1w scan pairs (HC Aß‐ = 179/MCI Aß+ = 98/AD Aß+ = 98) from AIBL&ADNeT were spatially normalised using SPM8 and SUVR normalised using the cerebellar cortex. PET scans were then quantified in 4 composite ROIs [Mesial‐Temporal (Me), Meta‐Temporal (MT), Temporo‐Parietal (TP) and Frontal (FT)] from a previously defined “universal” cortical mask. To anchor the 0 and 100 CTR, we only included HC Aß‐ (<10CL) and AD Aß+ (>25CL) individuals younger than 75y, with MMSE = 20, we also excluded HC participants with a quantification higher than the 75%tile in the Me and AD patients with a quantification lower than the 25%tile in the MT, resulting in 68 HC Aß‐ and 29 AD Aß+. We investigated two CTR scaling approaches using either a single transform based on the TP anchors to transform SUVR into CTR for all composites or using region‐based equations scaled with regional anchors.ResultThe mean and standard deviation (std) for the HC and AD groups are reported in Table 1. Using a single transformation resulted in the following equation: Ct = 100x(SUVR‐0.97)/2.26 Region‐based equations can be extrapolated from Table 1. Figures 1 and 2 show that regional CTR overstretches quantification in FT compared to single equation‐derived CTR. Thresholds set at 2 std above the HC were 2.38, 9.43, 7.66, 1.82, and 6.16 CTR for Me, MT, TP, FT and Global respectively, and were 7.05, 7.48, 7.66, 10.20, 7.68 CTR when using regional equation‐derived CTR.ConclusionThe region‐based approach provided slightly more consistent CTR distributions in the HC across the ROIs however, this approach tends to over‐stretch the CTR values in the frontal region.