Improving the stability of 11C–labeled L-methionine with ascorbate
Bibliographic record
Abstract
Carbon-11 labeled L-methionine ( 11 C–MET) is a popular tracer used in the clinic for imaging brain tumors with positron emission tomography. However, the stability of 11 C–MET in its final formulation is not well documented in literature. Recently, we observed fast degradation of HPLC-purified 11 C–MET over time, and systematic investigation was conducted to identify the cause. In this study, we verified the degraded product as 11 C–labeled methionine sulfoxide ( 11 C–METSO). To minimize oxidation, ascorbate (100 ppm) was added to the HPLC eluant, and the resulting HPLC-purified 11 C–MET was stable in the final formulation solution without noticeable degradation for up to 1 h after the end of synthesis. Our data suggest that to minimize degradation, ascorbate can be added to the 11 C–MET formulation solution especially if it is not administered into patients soon after the end of synthesis.
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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 | 0.001 | 0.001 |
| Meta-epidemiology (narrow) | 0.001 | 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 | 0.001 | 0.001 |
| 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 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".