HAI Book 2025 - Flipbook - Page 204
Aumont, Etienne
42
Increasing the granularity of tau-PET Braak staging using medial
temporal lobe segmentations to detect early memory impairment
Etienne Aumont1,2, Brandon Hall1,2,3, Lydia Trudel1,2,3, Tevy Chan1,2,3, Ali Hosseini1,2,3, Arthur
Macedo1,2,3, Jaime Fernandez Arias1,2,3, Nesrine Rahmouni1,2,3, Joseph Therriault1,2,3, Stijn
Servaes1,2,3, Gleb Bezgin1,2,3, Jenna Stevenson1,2,3, Pedro Rosa-Neto1,2,3
1
McGill University Research Centre for Studies in Aging, Montréal, QC, CA
Montreal Neurological Institute, Montréal, QC, CA
3
Department of neurology and neurosurgery, Montréal, QC, CA
2
Transforming brain images to a standard template has been a staple of tau PET processing. However, this
transformation comes at the cost of spatial specificity, which might be particularly important to study the small
medial temporal lobe (MTL) regions. This study aims to supplement traditional tau-PET Braak staging with native
space MTL tau-PET to identify early memory impairment better.
We segmented 6 MTL regions using T1-weighted images from 356 participants (60.1% female, aged 53-85 years)
using the Automatic Segmentation of Hippocampal Subfields algorithm (ASHS). With this, we generated native
space stages for [18F]MK6240 tau-PET images based on 2.5 standard deviation above the mean of 40 participants
aged 18-25. The three stages were based on 1) transentorhinal and entorhinal cortices; 2) anterior and posterior
hippocampus; 3) perirhinal and parahippocampal cortices. These stages were compared to standard-spacebased Braak stages. They were then combined to show differences in memory impairment measured with the Rey
Auditory Verbal Learning Test (RAVLT).
Native space stages tended to show earlier tau stages, with 14 participants reaching stage 1 while at Braak 0, and
21 at stage 3 and Braak II (Figure 1A). These two subgroups were designated as Braak stages 0.5 and 2.5,
respectively. The validity of these stages was supported by temporal meta-ROI elevation at stage 0.5 and 2.5
(Figure 1B). Stage 2.5 was the earliest showing significant impairment at the RAVLT delayed recall and learning
scores (p < 0.01; Figure 2).
HAI2025 - 204
