Can <i>T</i><sub>1</sub>w/<i>T</i><sub>2</sub>w ratio be used as a myelin‐specific measure in subcortical structures? Comparisons between FSE‐based <i>T</i><sub>1</sub>w/<i>T</i><sub>2</sub>w ratios, GRASE‐based <i>T</i><sub>1</sub>w/<i>T</i><sub>2</sub>w ratios and multi‐echo GRASE‐based myelin water fractions
Why this work is in the frame
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Bibliographic record
Abstract
Given the growing popularity of T 1 ‐weighted/ T 2 ‐weighted ( T 1 w/ T 2 w) ratio measurements, the objective of the current study was to evaluate the concordance between T 1 w/ T 2 w ratios obtained using conventional fast spin echo (FSE) versus combined gradient and spin echo (GRASE) sequences for T 2 w image acquisition, and to compare the resulting T 1 w/ T 2 w ratios with histologically validated myelin water fraction (MWF) measurements in several subcortical brain structures. In order to compare these measurements across a relatively wide range of myelin concentrations, whole‐brain T 1 w magnetization prepared rapid acquisition gradient echo (MPRAGE), T 2 w FSE and three‐dimensional multi‐echo GRASE data were acquired from 10 participants with multiple sclerosis at 3 T. Then, after high‐dimensional, non‐linear warping, region of interest (ROI) analyses were performed to compare T 1 w/ T 2 w ratios and MWF estimates (across participants and brain regions) in 11 bilateral white matter (WM) and four bilateral subcortical grey matter (SGM) structures extracted from the JHU_MNI_SS ‘Eve’ atlas. Although the GRASE sequence systematically underestimated T 1 w/ T 2 w values compared to the FSE sequence (revealed by Bland–Altman and mountain plots), linear regressions across participants and ROIs revealed consistently high correlations between the two methods ( r 2 = 0.62 for all ROIs, r 2 = 0.62 for WM structures and r 2 = 0.73 for SGM structures). However, correlations between either FSE‐based or GRASE‐based T 1 w/ T 2 w ratios and MWFs were extremely low in WM structures (FSE‐based, r 2 = 0.000020; GRASE‐based, r 2 = 0.0014), low across all ROIs (FSE‐based, r 2 = 0.053; GRASE‐based, r 2 = 0.029) and moderate in SGM structures (FSE‐based, r 2 = 0.20; GRASE‐based, r 2 = 0.17). Overall, our findings indicated a high degree of correlation (but not equivalence) between FSE‐based and GRASE‐based T 1 w/ T 2 w ratios, and low correlations between T 1 w/ T 2 w ratios and MWFs. This suggests that the two T 1 w/ T 2 w ratio approaches measure similar facets of subcortical tissue microstructure, whereas T 1 w/ T 2 w ratios and MWFs appear to be sensitized to different microstructural properties. On this basis, we conclude that multi‐echo GRASE sequences can be used in future studies to efficiently elucidate both general ( T 1 w/ T 2 w ratio) and myelin‐specific (MWF) tissue characteristics.
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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 | 0.005 | 0.003 |
| Meta-epidemiology (narrow) | 0.007 | 0.006 |
| Meta-epidemiology (broad) | 0.008 | 0.002 |
| Bibliometrics | 0.007 | 0.010 |
| Science and technology studies | 0.003 | 0.006 |
| Scholarly communication | 0.001 | 0.002 |
| Open science | 0.003 | 0.001 |
| Research integrity | 0.004 | 0.009 |
| Insufficient payload (model declined to judge) | 0.000 | 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 it