Abstract 9803: Optimization and Comparison of Myocardial T1 Techniques at 3T in Patients With Aortic Stenosis

Abstract

BACKGROUND: T1 mapping is an emerging cardiac magnetic resonance imaging technique to assess diffuse myocardial fibrosis. However, the optimal approach remains uncertain, especially at 3T. We sought to optimize and compare the most widely-used techniques. METHODS: 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) and interstitial contrast volume of distribution (Vd) 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. RESULTS: There was no segmental variation across the ventricle in any of the T1 measures evaluated. λ and Vd did not vary with time, while post-contrast T1 was relatively constant between 15-30min. Thus, mid-cavity myocardium at 20min was used for subsequent analyses. Vd 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, Vd and λ were both higher in patients with AS compared to controls (Vd 28.3±1.7 versus 26.0±1.6%, p <0.001; λ 0.46±0.03 versus 0.44±0.03, p =0.02) (Figure 1A). By comparison, scan-rescan reproducibilities for pre- and post-contrast myocardial T1 values were only modest (ICC 0.72 and 0.56) with no differences observed between cases and controls (both p>0.05) (Figure 1B). CONCLUSIONS: We recommend Vd and λ to assess diffuse myocardial fibrosis at 3T based upon their superior reproducibility and ability to identify disease states.