The effects of an initial depolarization pulse on dissolved phase hyperpolarized <sup>129</sup>Xe brain MRI
Bibliographic record
Abstract
Purpose To evaluate the effect of an initial 90° depolarization RF pulse on the dissolved‐phase hyperpolarized (HP) xenon‐129 ( 129 Xe) brain imaging and to compare the SNR variability of HP 129 Xe images acquired without an initial depolarization RF pulse to those following the initial depolarization pulse. Methods Five cognitive normal healthy volunteers were imaged using a Philips Achieva 3.0T MRI scanner during a single breath‐hold following inhalation of 1 L of HP 129 Xe. Each participant underwent six HP 129 Xe scans. Three scans were performed using conventional single‐slice projection HP 129 Xe brain imaging, and the other three scans were performed using the HP 129 Xe time‐of‐flight imaging with an initial rectangular depolarization pulse. Results Although the utilization of an initial depolarization results in the reduction of the mean image SNR, the presence of an initial depolarization RF pulse reduces the SNR variability of the HP 129 Xe brain image by a factor of 2.26. The highest SNR variability was observed from the posterior brain region, where the anterior region possessed the lower level of signal variability. Conclusion An initial 90° depolarization RF pulse, applied prior to the HP 129 Xe image acquisition, reduced the HP 129 Xe signal variability more than two times between the different breath‐hold images.
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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) | 0.000 | 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) | 0.000 | 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".