TH‐D‐201C‐10: Improved Quantification of the CH2/CH3 Ratio of Lipids: Illustration in Vivo on Tibial Bone Marrow at 3 T
Bibliographic record
Abstract
Purpose: To improve the accuracy of lipid CH2/CH3 ratios determined by proton magnetic resonance spectroscopy (MRS) by minimizing J‐coupling modulations of the CH3 lipid peak. Method and Materials: Experiments were conducted in vivo on the tibial bone marrow lipids of four volunteers at 3 T. A regular PRESS (Point RESolved Spectroscopy) sequence was used to estimate the T2 (transverse relaxation) of the CH2 protons by acquiring spectra at five echo times (TEs) and plotting the areas as a function of TE. The curve was fitted to the function Moexp(−TE/T2) where M0 is proportional to the CH2 proton concentration. The CH3 response to a regular PRESS sequence is modulated due to J‐coupling interactions and does not decay monotonically. To determine Mo of the CH3 protons a narrow‐bandwidth PRESS sequence was designed that rewinds the J‐coupling evolution of the CH3 protons in the voxel of interest and spectra were acquired with the same five TEs. The CH2/CH3 ratio was calculated by dividing the CH2 Mo by that determined for CH3 and the result was multiplied by 1.5 to compensate for the different proton multiplicities. Results: The mean T2 of the CH2 protons was estimated to be ≈ 88 ms. Applying the narrow‐bandwidth PRESS sequence minimized CH3 signal variations due to J‐coupling and resulted in a decay curve that could be described by a monoexponential T2 decay function. The mean T2 for the CH3 protons was ≈ 133 ms. A mean ratio of 12:1 was calculated for the CH2:CH3 ratio of the tibial bone marrow lipids of all volunteers. Conclusion: The presented PRESS sequence enables the T2 of the CH3 lipid protons to be measured with more accuracy than would be determined by using short‐TEs thereby allowing a more accurate measure of the CH2/CH3 lipid composition ratio to be determined.
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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 | 0.001 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.001 | 0.000 |
| Research integrity | 0.002 | 0.001 |
| 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".