Pulse‐wave velocity measured in one heartbeat using MR tagging
Bibliographic record
Abstract
A noninvasive method for measuring the aortic pulse-wave velocity (PWV) in a single heartbeat is introduced. The method sinusoidally tags a column of blood within the vessel, and rapidly acquires a series of 1D projections of the tags as they move (in practice, 64 projections at 4-ms intervals). From these projections, the relative motion of blood at different positions along the vessel is measured. The PWV is obtained by fitting a mathematical model of blood flow to the tag trajectories. Tests of this method in a pulsatile flow phantom are presented using latex and polyurethane tubes. The PWV measured in these tubes was (mean +/- standard deviation) 4.4 +/- 0.5 m/s and 2.3 +/- 0.2 m/s, respectively. The distensibility of each tube was calculated from the PWV (latex = (7 +/- 2) 10(-3) mm Hg(-1), poly. = (25 +/- 4) 10(-3)mmHg(-1)) and found to agree within error with distensibility measurements based on the change of tube area with pressure (latex = (6.3 +/- 0.3) 10(-3)mmHg(-1), poly. = (27 +/- 1) 10(-3) mmHg(-1)). To test its feasibility, the PWV measurement was applied to four normal volunteers. The measured PWV values were 3.9 +/- 0.8 m/s, 3.6 +/- 0.9 m/s, 3.9 +/- 0.5 m/s, and 5.3 +/- 0.8 m/s. By acquiring an independent PWV measurement each heartbeat, errors introduced by arrhythmia and trigger variability appear to be avoided with this method.
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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 | 0.000 | 0.000 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.001 | 0.000 |
| Bibliometrics | 0.000 | 0.001 |
| 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 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".