PRESS timings for resolving <sup>13</sup>C<sub>4</sub>‐glutamate <sup>1</sup>H signal at 9.4 T: Demonstration in rat with uniformly labelled <sup>13</sup>C‐glucose
Bibliographic record
Abstract
MRS of 13C4‐labelled glutamate (13C4‐Glu) during an infusion of a carbon‐13 (13C)‐labelled substrate, such as uniformly labelled glucose ([U‐13C6]‐Glc), provides a measure of Glc metabolism. The presented work provides a single‐shot indirect 13C detection technique to quantify the approximately 2.51 ppm 13C4‐Glu satellite proton (1H) peak at 9.4 T. The methodology is an optimized point‐resolved spectroscopy (PRESS) sequence that minimizes signal contamination from the strongly coupled protons of N‐acetylaspartate (NAA), which resonate at approximately 2.49 ppm. J‐coupling evolution of protons was characterized numerically and verified experimentally. A (TE1, TE2) combination of (20 ms, 106 ms) was found to be suitable for minimizing NAA signal in the 2.51 ppm 1H 13C4‐Glu spectral region, while retaining the 13C4‐Glu 1H satellite peak. The efficacy of the technique was verified on phantom solutions and on two rat brains in vivo during an infusion of [U‐13C6]‐Glc. LCModel was employed for analysis of the in vivo spectra to quantify the 2.51 ppm 1H 13C4‐Glu signal to obtain Glu C4 fractional enrichment time courses during the infusions. Cramér‐Rao lower bounds of about 8% were obtained for the 2.51 ppm 13C4‐Glu 1H satellite peak with the optimal TE combination.
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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 | 0.000 | 0.001 |
| 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 | 0.001 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.001 | 0.000 |
| Insufficient payload (model declined to judge) | 0.002 | 0.001 |
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".