Aging and gender effects in native T1 and extracellular volume fraction assessment using SASHA
Bibliographic record
Abstract
Reference values for T 1 mapping-derived extracellular volume fraction (ECV) in healthy individuals are not currently well established. Histological measurements in autopsy studies have shown decreasing ECV with healthy aging in men, however recent non-invasive measurements of ECV using different T 1 mapping techniques are inconsistent with respect to the effect of aging and gender, with a relatively wide range of values depending on the method. The goal of the current study was to characterize native T 1 and ECV as a function of age in healthy individuals (no cardiovascular risk factors or medication) with the SAturation-recovery single-SHot Acquisition (SASHA) method (Magn Reson Med. 2014 Jun;71(6):2082-95), providing comparison to existing literature. Well characterized healthy individuals from the Alberta HEART study (BMC Cardiovasc Disord. 2014 Jul 25;14:91) underwent CMR on a Siemens 1.5T system (Sonata, Avanto) with T 1 measurements using the SASHA pulse sequence. Imaging was performed on a mid-ventricular short-axis slice at baseline (pre-contrast) and ~15 minutes after intravenous administration of 0.15 mmol/kg gadobutrol. ECV was measured in the ventricular septum, calculated as (1-hct)*(Myocardium ΔR 1 )/(Blood ΔR 1 ), where ΔR 1 is 1/T 1 post - 1/T 1 pre, and hct was the most recent hematocrit. Native T 1 and ECV measures were available from 44 individuals (60.7 ± 9.6 years, range 43-80, 15 male) free from cardiovascular disease, diabetes, hypertension, and not on any cardiovascular medication. Average native myocardial T 1 value was 1189 ± 38 ms, which was increased in women compared to men (1201 ± 29 vs. 1167 ± 44 ms, p < 0.05), however did not vary significantly with age (Figure 1A ; p = 0.59). Average ECV was 22 ± 2% (range 18-28%), and did not vary significantly with age (Figure 1B ; p = 0.20) or gender (men: 21 ± 2% vs. women: 22 ± 2%; p = 0.14). SASHA ECV values were similar to a previous histology (p > 0.05) study. SASHA native T 1 values were higher and SASHA ECV values were lower than inversion recovery based techniques in groups free of cardiovascular risk factors (native T 1 comparisons only for 1.5T; p < 0.05 for all comparisons) (Table 1 ). Gender and age effects are noted to be different between methods (Table 1 ). A) SASHA native T 1 values vs. age . B) SASHA extracellular volume fraction (ECV) vs. age. SASHA ECV values showed no dependence on age or gender and were 14-27% smaller as compared to inversion-recovery techniques, but with good general agreement to histological studies. SASHA native T 1 times are 19-20% longer than inversion-recovery techniques, and though they are longer in women, there is no age dependence. Significantly different ECVs by method reflect systematic differences in blood and myocardial T 1 values (native and post-contrast), consistent with previous reports (Kellman, J Cardiovasc Magn Reson. 2014 Jan 4;16:2). Discrepancies in the relationship between native T 1 and ECV by age and gender warrant more detailed comparison of methods as the field moves towards universal age/gender reference values.
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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) | 0.000 | 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 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".