Associations between brain TSPO and [<sup>18</sup>F]FDG‐PET signals in neurodegenerative disorders
Bibliographic record
Abstract
Abstract Background Recent evidence indicates that activated microglial cells contribute to the brain FDG‐PET signal changes in neurodegenerative disorders. Radiopharmaceuticals targeting the 18‐kDa translocator protein (TSPO) have been used to measure microglial activation. The combination of FDG‐PET and TSPO‐PET allows for assessing, in‐vivo and non‐invasively, whether they associate in brain regions vulnerable to neurodegeneration. So far, multiple studies have used FDG‐PET and TSPO‐PET concomitantly, but to our knowledge, no systematic evaluation has been conducted to assess whether they are associated. We aimed to systematically summarize the current data on brain TSPO‐PET and FDG‐PET signals in individuals with neurodegenerative disorders. Method Studies performing TSPO‐ and FDG‐PET in neurodegenerative disorders were searched in PubMed and Web of Science. Included articles must have performed PET images concomitantly with both tracers in healthy controls and individuals presenting with neurodegenerative disorders. This review complied with PRISMA (2020) guidelines and was registered at PROSPERO (CRD42022354523). Result A total of 272 articles were found after a search on PubMed and Web of Science, with eight meeting the inclusion criteria. We included clinical studies with individuals presenting Alzheimer’s Disease (AD), Parkinson’s Disease (PD), corticobasal syndrome and progressive supranuclear palsy, behavioral variant frontotemporal dementia, and progressive nonfluent aphasia. In AD, five studies presented negative associations, and one presented a positive association between TSPO and FDG signals in brain regions vulnerable to AD. In PD (3 studies) and the other related neurodegenerative disorders (2 studies) evaluated, we found a negative correlation between FDG‐PET and TSPO‐PET signals in vulnerable regions. Conclusion All studies presented associations between FDG‐ and TSPO‐PET signals. These findings suggest that microglia, indexed by TSPO binding, negatively impacts brain glucose metabolism indexed by FDG‐PET. Further studies are needed to address associations between TSPO‐PET and FDG‐PET in the asymptomatic and early stages of neurodegenerative disorders.
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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 | 0.003 | 0.013 |
| Meta-epidemiology (narrow) | 0.001 | 0.000 |
| Meta-epidemiology (broad) | 0.004 | 0.002 |
| Bibliometrics | 0.014 | 0.016 |
| Science and technology studies | 0.000 | 0.001 |
| Scholarly communication | 0.002 | 0.002 |
| Open science | 0.001 | 0.001 |
| Research integrity | 0.001 | 0.001 |
| Insufficient payload (model declined to judge) | 0.004 | 0.000 |
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".