Assessment of intracranial blood flow velocities using a computer controlled vasoactive stimulus: A comparison between phase contrast magnetic resonance angiography and transcranial doppler ultrasonography
Bibliographic record
Abstract
PURPOSE: To compare measurements of blood flow velocity (BFV) and BFV changes in the middle cerebral arteries (MCA) acquired from phase contrast magnetic resonance angiography (PCMRA) and transcranial Doppler ultrasound (TCD) during controlled manipulation of end-tidal partial pressure of carbon dioxide (PetCO2 ). MATERIALS AND METHODS: In vivo TCD and PCMRA velocity data from the M1 segment in the MCA of nine healthy adult volunteers were acquired during precise targeting of PetCO2 induced by a computer-controlled gas delivery system. Doppler spectra and phase contrast data were processed into time-averaged peak-velocity (TAPV) values for comparison. Changes in velocity between baseline and hypercapnia were analyzed in terms of velocity-based cerebrovascular reactivity (CVR). RESULTS: Good correlation between the pairs of velocity measurements acquired from the two modalities were found (ρ = 0.81), but Bland-Altman analysis indicates a significant bias error. There was relatively weak agreement between the pairs of computed CVR values (ρ = -0.26). CONCLUSION: Under precise PetCO2 control, PCMRA proves to be more consistent than TCD. Despite issues with variability, TCD is qualitatively comparable to PCMRA measures of velocity in the MCA. However, PCMRA velocity results are better suited for analyses that require quantitative values, such as CVR.
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How this classification was reachedexpand
Full frame distilled prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. Learned from the 10,348 direct Codex labels and 10,348 direct Gemma labels. Candidate is the union of thresholded teacher heads; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels or direct frontier model labels.
Codex and Gemma teacher scores by category
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.001 | 0.000 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.002 | 0.001 |
| Bibliometrics | 0.001 | 0.001 |
| Science and technology studies | 0.000 | 0.001 |
| Scholarly communication | 0.000 | 0.001 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.001 |
| Insufficient payload (model declined to judge) | 0.000 | 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 teacher head, 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".