Blood‐oxygen level dependent MRI measures of cerebrovascular reactivity using a controlled respiratory challenge: Reproducibility and gender differences
Bibliographic record
Abstract
PURPOSE: To evaluate the reproducibility and gender differences in cerebrovascular reactivity (CVR) measurements obtained using the blood-oxygen level dependent (BOLD) response to controlled changes in end-tidal partial pressure of carbon dioxide (PETCO(2)). MATERIALS AND METHODS: We obtained ethical approval to image 19 healthy volunteers (10 men, 9 women) on a 1.5 Tesla (T) MRI scanner twice on two separate days using identical procedures. CVR images were generated by collecting BOLD MRI data during controlled changes in PETCO(2) induced by a sequential gas delivery system. RESULTS: Using the intraclass correlation coefficient (ICC), we demonstrated excellent within-day CVR measures in gray matter (GM) (ICC = 0.92) and white matter (WM) (ICC = 0.88) regions, excellent between-day reproducibility in GM (ICC = 0.81), and good between-day reproducibility in the WM (ICC = 0.66). CVR values between men and women were significantly different in the GM and WM. Men exhibited a 22 +/- 2% greater CVR in GM and a 17 +/- 2% greater CVR in WM compared with females. CONCLUSION: Our results demonstrate the reliability of BOLD MRI CVR measurements obtained using a controlled cerebrovascular challenge. Using this technique, we also revealed significantly increased BOLD response to CO(2) in males compared with females.
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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 | 0.004 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.000 | 0.000 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.001 | 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".