HAI Book 2025 - Flipbook - Page 240
Rahmouni, Nesrine
55
Association between early and late tau aggregation across tau
imaging agents: The HEAD Study
Nesrine Rahmouni1, Cécile Tissot2, Joseph Therriault1, Ali Hosseini1, Arthur Macedo1, Stijn
Servaes1, Firoza Lussier3, Lydia Trudel1, Brandon Hall1, Jaime Fernandez-Arias1, Yi-Ting
Wang1, Jenna Stevenson1, Serge Gauthier1, Suzanne Baker2, Tharick A. Pascoal3, Pedro RosaNeto1
1
McGill University, Montreal, QC, CA
Lawrence Berkeley National Laboratory, Berkeley, CA, US
3
University of Pittsburgh, Pittsburgh, PE, US
2
Background: The association between medial temporal and neocortical SUVR depends on availability of cortical
tau. However, tracer differences in affinity and off-target binding might interfere in these associations. Here, we
examined the association between medial temporal and neocortical SUVR using voxel-based approach.
Methods: We included 68 individuals (46 Cognitively Unimpaired and 22 Cognitively Impaired) from the HEAD
Study recruited at McGill University. All individuals were assessed for amyloid-´ (A´) deposition using
[18F]AZD4694-PET and four tau-PET ligands ([18F][18F]MK6240, [18F]Flortaucipir, [18F]RO948 and [18F]PI-2620).
Correlation maps evaluated the relationship between PET tracers9 uptake in the entorhinal cortex (EC), in the
inferior temporal gyrus and in the posterior cingulate and their association with the tracer9s uptake in later Braak
regions. Correlations coefficients were compared across Braak Stages.
Results: Positive associations were observed between tau-PET SUVR in the EC (Figure1). [18F]MK6240 EC was
correlated with tracer uptake in the whole cortex. [18F] Flortaucipir was associated with tracer uptake in similar
regions, albeit showing a lower t-value. [18F]PI2620 EC uptake correlated with binding in regions Braak II-V. Finally,
[18F]RO948 was associated with uptake. Across Braak regions, entorhinal seed covariance maps are restricted to
early Braak regions in A´- individuals, while encompassing neocortical regions in A´+ individuals (Figure 2).
Finally, seeds outside the MTL reflected advanced tau covariance patterns in A´+ individuals, with [18F]MK6240
showing stronger correlation patterns in all Braak regions, followed by [18F] Flortaucipir, [18F]RO948 and
[18F]PI2620 (Figure 3).
Conclusion: [18F]MK6240 showed higher and more widespread correlations between early and late tau pathology,
potentially due to this tracer9s higher affinity for tau tangles. Results were concordant at the voxel and region-oninterested levels. [18F] Flortaucipir, [18F]RO948 and [18F]PI-2620 showed similar results, in lower magnitude.
HAI2025 - 240
