P2‐374: CORRELATION OF QUANTITATIVE SUSCEPTIBILITY MAPPING AND COGNITIVE DYSFUNCTION IN MIXED ALZHEIMER'S AND VASCULAR DEMENTIA
Bibliographic record
Abstract
The coexistence of Alzheimer's disease (AD) and vascular dementia (VaD) is the most common type of mixed dementia (MD). More than half of all clinically diagnosed AD cases show multiple pathologies at autopsy, but these are challenging to diagnose premortem. Hallmark features of MD are known to include white-matter disease (WMD) and deep grey matter (dGM) microbleeds, but in-vivo imaging markers to identify and characterize these features are needed. Quantitative susceptibility mapping (QSM), a magnetic resonance imaging (MRI) measure that maps magnetic tissue properties and alterations (e.g. related to iron and myelin), may be able to fill this gap. Objective: To evaluate the relationship between QSM and clinical/cognitive measures in participants with clinically diagnosed MD, AD or subcortical VaD (SVaD). In this cross-sectional study, participants (N=17) were scanned at 3T (subtypes:7 MD/5 SvaD/5 AD; Sex:11M/6F; Age:75±8; MoCa:19±4 (range:12-28)). Multi-echo gradient echo data were acquired for QSM, including 5 echoes with 0.49x0.49x1mm voxels. QSM data were processed using in-house developed software. Median QSM values were calculated within basal ganglia masks, containing the putamen, pallidum, accumbens and caudate as defined by the Harvard-Oxford subcortical atlas. Basal ganglia volumes were computed from the individual region-of-interest masks. Clinical/cognitive assessments included Clinical Dementia Rating (CDR) sum of boxes and Montreal Cognitive Assessment (MoCA) total score. We used a general linear model to predict clinical/neuropsychological assessment scores from basal ganglia QSM measurements. Covariates included age, sex, presence of cardiovascular conditions (to account for the effect of hypertension) and basal ganglia volumes. Both increasing age (β=−0.4; p=0.001) and increasing basal ganglia QSM (β=-194; p=0.002) were significantly associated with lower MoCA total scores (model R=0.6). The CDR sum of boxes measure was not significantly correlated with the basal ganglia QSM. There were no significant differences in basal ganglia volumes or QSM measures between MD, SVaD and AD after adjusting for age and sex. Our findings indicate that increasing dGM iron concentration, or the potential presence of microbleed-related pathologies, could be associated with cognitive deficits in dementia. Larger follow-up studies with sufficient power are warranted to separate MD from other dementias.
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How this classification was reachedexpand
Full frame machine prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. The Gemma side is a direct model label for every work in the frame, read from the title-only record. The Codex side is a classifier learned from the 10,348 direct Codex labels and calibrated to design-weighted sample rates; fields without enough sample support carry no Codex call. Candidate is the union of the two sides; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels.
Distilled classifier scores by category (both heads)
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.000 | 0.002 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.001 | 0.000 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.001 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.001 | 0.000 |
| Insufficient payload (model declined to judge) | 0.004 | 0.001 |
Machine scores (provisional)
The two teacher heads of the student model, read on this work. A score orders the frame for review; it never asserts a category, and the validation status ships verbatim with every row.
Baseline scores from an immature model (maturity gate not passed, 7 training rounds). Scores rank; they never assert a category.
score_only:v0-immature-baseline · verbatim from the scoring run: score_only means the number may rank works, and no category label ships from itClassification
machine, unvalidatedMachine predicted; a candidate call from one source (direct Gemma or distilled Codex), not a consensus.
How this classification was reached, model by model and score by score, is at the end of the page under "How this classification was reached".