<i>J</i>‐difference editing of gamma‐aminobutyric acid (GABA): Simulated and experimental multiplet patterns
Bibliographic record
Abstract
PURPOSE: To investigate factors that influence the multiplet pattern observed in J-difference editing of gamma-aminobutyric acid (GABA). METHODS: Density matrix simulations were applied to investigate the shape of the 3 ppm GABA multiplet as a function of the editing sequence's slice-selective refocusing pulse properties, in particular bandwidth, transition width, and flip angle. For comparison to the calculations, experimental measurements were also made at 3 T on a 10 mM GABA solution using the MEGA-PRESS sequence at various refocusing pulse flip angles. RESULTS: Good agreement was found between experiments and simulations. The edited multiplet consists of two outer lines of slightly unequal intensity due to strong coupling, and a smaller central line, the result of the unequal J-couplings between the C4 and C3 protons. The size of the center peak increases with increasing slice-selective refocusing pulse transition width, and deviation of the flip angle from 180°. CONCLUSION: The 3 ppm GABA multiplet pattern observed in the MEGA-PRESS experiment depends quite strongly on the properties of the slice-selective refocusing pulses used. Under some circumstance, the central peak can be quite large; this does not necessarily indicate inefficient editing, or a subtraction artifact, but should be recognized as a property of the pulse sequence itself.
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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) | 0.001 | 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".