Pilot study of MRI white matter tissue properties in Alzheimer’s, vascular and mixed dementias
Bibliographic record
Abstract
Abstract Background Alzheimer’s disease (AD) with cerebrovascular disease is known as ‘mixed’ dementia (MixD).[Wang_2012][Langa_2004] MixD can have heterogeneous clinical/imaging presentations. This makes it difficult to distinguish MixD from AD or vascular dementia (VaD) using structural markers such as atrophy or white matter hyperintensity (WMH) volumes. [Suri_2014] We explored whether WM tissue properties on MRI, represented by R2* and diffusion‐tensor (DTI) images, could distinguish MixD from AD or VaD. Method N=17 participants (cross‐sectional; 7 MixD/5 Subcortical VaD/5 AD; Sex: 11M/6F; Age: 75±8yrs) were scanned on a 3T Philips Achieva. WMHs were segmented on 3D‐Fluid Attenuated Inversion Recovery images. T1‐weighted MP‐RAGE images were segmented into the grey/white‐matters using SPM12. These outputs were combined to construct WMH and normal‐appearing WM (NAWM) masks. DTI images were processed using FSL. R2* images were computed using in‐house software. For each participant, the average R2*, fractional anisotropy (FA) and mean diffusivity (MDf) values were calculated within the WMH and NAWM masks. Result Average WMH volumes were (mean±SD) AD: 5191±4693mm3, MD: 34680±17059mm3 (p<.05 compared to AD), SVaD: 20896±14920mm3 (p>.05 compared to MixD or AD). A linear model was used to predict the measured R2*, FA or MDf values from the diagnosis subtypes, adjusting for age and sex. R2* results: Pairwise t‐tests revealed significantly lower R2* values within the WMHs compared to NAWM (all subtypes p<0.0005). MixD had significantly lower WMH R2* values compared to AD (p=0.01) or VaD (p=0.02) subgroups. DTI results: Pairwise t‐tests revealed significantly higher MDf values within the WMHs compared to NAWM (all subtypes p<0.009). FA values were significantly lower within the WMHs compared to NAWM for the MixD (p=0.0002) and VaD (p=0.03) but not the AD (p=0.09) subtype. Conclusion Our MixD cohort was characterized by potentially disrupted fiber integrity (represented by decreased FA) and increased water content (represented by lower R2*) within the WMH areas. These abnormalities likely represent etiologies caused by both neurodegenerative and cerebrovascular factors. Future studies that incorporate measures of neurodegeneration or neuroinflammation, such as biofluid markers, may help to further characterize WM tissue abnormalities in MixD compared to those found in ‘pure’ AD or VaD.
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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 | 0.001 | 0.002 |
| Meta-epidemiology (narrow) | 0.001 | 0.000 |
| Meta-epidemiology (broad) | 0.001 | 0.000 |
| Bibliometrics | 0.001 | 0.000 |
| Science and technology studies | 0.001 | 0.000 |
| Scholarly communication | 0.001 | 0.001 |
| Open science | 0.000 | 0.001 |
| Research integrity | 0.001 | 0.000 |
| Insufficient payload (model declined to judge) | 0.003 | 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".