Diffusion Tensor Imaging along the Perivascular Space for Characterizing Cerebral Interstitial Fluid Dynamics in Alzheimer Disease: A Systematic Review and Meta-Analysis
Bibliographic record
Abstract
ABSTRACT BACKGROUND: Diffusion Tensor Imaging along the Perivascular Space (DTI-ALPS) has emerged as a measure of cerebral interstitial fluid dynamics, a proposed component of the glymphatic system, which may provide insight into central nervous system fluid transport and waste clearance. PURPOSE: Our study aimed to evaluate whether DTI-ALPS can serve as a reliable, noninvasive imaging biomarker of altered interstitial fluid dynamics across the Alzheimer’s Disease (AD) continuum. DATA SOURCES: We searched Scopus, Web of Science, and PubMed for articles published through October 2024. STUDY SELECTION: Studies were included if they reported the ALPS-index in AD, mild cognitive impairment (MCI), and healthy control groups. Studies were excluded if they lacked sufficient data or involved overlapping cohorts. DATA ANALYSIS: Using standardized mean difference (SMD), we compared the ALPS-index in AD and MCI groups to healthy controls. We assessed the association between the ALPS index and cognitive function using a random-effects model. A qualitative risk bias assessment was conducted using the Newcastle-Ottawa Scale (NOS). DATA SYNTHESIS: Nineteen studies met the inclusion criteria. The overall ALPS index was significantly lower in AD subjects than in healthy controls (SMD = -1.07, 95% CI: -1.57 to -0.56). Statistically significant differences were also observed between AD and MCI subjects (SMD = -0.25, 95% CI: -0.40 to -0.10), as well as between MCI and healthy control subjects (SMD = -0.81, 95% CI: -1.57 to 0.06). Additionally, the ALPS index showed a statistically significant association with Mini-Mental State Examination scores (pooled correlation effect size = 0.43, 95% CI: 0.28 to 0.57). A negative correlation was also observed between the ALPS index and amyloid deposition on PET, with a pooled correlation effect size of -0.42 (95% CI: -0.66 to -0.19, p < 0.001). LIMITATIONS: Potential limitations include heterogeneity across imaging protocols, variability in cognitive assessments, and possible publication bias. CONCLUSIONS: The DTI-ALPS technique showed significant differences among cognitive groups across the AD continuum and was associated with cognitive scores and brain amyloidosis. This provides further evidence that DTI-ALPS could be useful in detecting altered cerebral interstitial fluid dynamics in MCI and AD. ABBREVIATIONS: AD＝ Alzheimer’s disease; Aβ＝ beta-amyloid; PET＝ positron emission tomography; PiB＝ Pittsburgh Compound B; FBB＝ Florbetaben; CL＝ Centiloid.
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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 | 0.017 | 0.048 |
| Meta-epidemiology (narrow) | 0.002 | 0.001 |
| Meta-epidemiology (broad) | 0.015 | 0.023 |
| Bibliometrics | 0.007 | 0.009 |
| Science and technology studies | 0.001 | 0.001 |
| Scholarly communication | 0.003 | 0.002 |
| Open science | 0.002 | 0.002 |
| Research integrity | 0.002 | 0.002 |
| Insufficient payload (model declined to judge) | 0.005 | 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".