P2‐094: Correlating imaging with language impairment in degenerative dementias: How well do PIB and FDG PET match behavior?
Bibliographic record
Abstract
Alzheimer's Disease (AD) has a typical course characterized by prominent memory impairment while in Primary Progressive Aphasia (PPA) language problems can be the primary or sole deficit. While PPA can be a clinical manifestation of frontotemporal dementia pathology (tauopathy or tardopathy), in a particular subgroup, termed Logopenic Primary Progressive Aphasia, AD is often the underlying pathology despite the “focality” of the cognitive deficit. We wondered whether multi-modal imaging with Flouro-deoxyglucose PET (FDG) and C-11 amyloid PET imaging with Pittsburgh B Compound (PIB) would demonstrate different lesion localizations between these AD groups in a coherent fashion. We hypothesized that these imaging modalities would be convergent, and usually all point in the direction of AD (bilateral deficits) vs. PPA(strictly left temporal/frontal deficits). Fourteen subjects with typical AD and 12 with PPA-LV were studied. MRI was assessed visually and with VBM of grey matter. FDG-PET scans were assessed as typical AD [ ie., bitemporo-parietal decreased glucose uptake] or left predominant pattern of decreased metabolism, on clinical as well as SUVR analysis. PIB PET amyloid imaging was considered positive if there was SUVR >1.5 for association cortex regions, corresponding to medium or large PIB uptake on visual inspection. Similar patterns of PIB deposition - on visual analysis as well as SUVR comparison - were assessed. On MRI scan, 12/14 ADs and 6/12 PPA-LVs showed hippocampalatrophy; 4/14 ADs and 6/12 PPA-LVs showed predominantly left sided cortical atrophy. On FDG PET scanning, 5/12 ADs and 10/12PPA-LVs showed predominantly left sided hypometabolism. On PIB PET scanning, there was no visual or SUVR difference between left sided PIB uptake between the two sets of individuals. There was no significant left PIB predominance in either group. Among those clinically labeled as PPA-LV, amyloid imaging with PIB showed no particular differences from typical AD individuals - amyloid was seen on both sides of the brain. MRI and FDG PET both showed left sided abnormalities more commonly (but not exclusively) in the PPA-LV group compared to typical AD individuals. There was overlap in all modalities between imaging modalities. FDG PET appears most reliably to mirror cognitive deficits, in that the pattern in PPA-LV subjects showed the greatest differences from typical AD subjects. Supported by the CIHR (Canadian Institutes of Health Research), and the FRSQ Quebec Aging Network (RQRV).
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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 | 0.002 | 0.007 |
| Meta-epidemiology (narrow) | 0.001 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.002 | 0.001 |
| Science and technology studies | 0.000 | 0.001 |
| Scholarly communication | 0.001 | 0.001 |
| Open science | 0.001 | 0.001 |
| Research integrity | 0.001 | 0.000 |
| Insufficient payload (model declined to judge) | 0.002 | 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".