Which T1 mapping approach at 3T is optimal for assessing myocardial fibrosis and differentiating asymptomatic aortic stenosis patients from healthy volunteers?
Extracellular volume fraction (ECV) is a highly reproducible measure of diffuse myocardial fibrosis at 3T MRI that effectively differentiates patients with aortic stenosis from healthy individuals.
AIMS: To determine the optimal T1 mapping approach to assess myocardial fibrosis at 3T. METHODS AND RESULTS: T1 mapping was performed at 3T using the modified look-locker-inversion sequence in 20 healthy volunteers and 20 patients with aortic stenosis (AS). Pre- and post-contrast myocardial T1, the partition coefficient (λ; ΔRmyocardium/ΔRblood, where ΔR = 1/post-contrast T1 - 1/pre-contrast T1), and extracellular volume fraction ECV; λ (1 - haematocrit) were assessed. After establishing the optimal time point and myocardial region for analysis, we compared the reproducibility of these T1 measures and their ability to differentiate asymptomatic patients with AS from healthy volunteers. There was no segmental variation across the ventricle in any of the T1 measures evaluated. λ and ECV did not vary with time, while post-contrast T1 was relatively constant between 15 and 30 min. Thus, mid-cavity myocardium at 20 min was used for subsequent analyses. ECV displayed excellent intra-, inter-observer, and scan-rescan reproducibility intra-class correlation coefficients (ICC) 1.00, 0.97, and 0.96, respectively, as did λ (ICC 0.99, 0.94, 0.93, respectively). Moreover, ECV and λ were both higher in patients with AS compared with controls (ECV 28.3 ± 1.7 vs. 26.0 ± 1.6%, P 0.05). CONCLUSIONS: ECV appears to be the most promising measure of diffuse myocardial fibrosis at 3T based upon its superior reproducibility and ability to differentiate disease from health.
Chin et al. (Mon,) studied this question.