Myocardial T1-mapping at 3T using saturation-recovery: reference values, precision and comparison with MOLLI.

ABSTRACT

BACKGROUND: Myocardial T1-mapping recently emerged as a promising quantitative method for non-invasive tissue characterization in numerous cardiomyopathies. Commonly performed with an inversion-recovery (IR) magnetization preparation at 1.5T, the application at 3T has gained due to increased quantification precision. Alternatively, saturation-recovery (SR) T1-mapping has recently been introduced at 1.5T for improved accuracy. Thus, the purpose of this study is to investigate the robustness and precision of SR T1-mapping at 3T and to establish accurate reference values for native T1-times and extracellular volume fraction (ECV) of healthy myocardium. METHODS: Balanced Steady-State Free-Precession (bSSFP) Saturation-Pulse Prepared Heart-rate independent Inversion-REcovery (SAPPHIRE) and Saturation-recovery Single-SHot Acquisition (SASHA) T1-mapping were compared with the Modified Look-Locker inversion recovery (MOLLI) sequence at 3T. Accuracy and precision were studied in phantom. Native and post-contrast T1-times and regional ECV were determined in 20 healthy subjects (10 men, 27 ± 5 years). Subjective image quality, susceptibility artifact rating, in-vivo precision and reproducibility were analyzed. RESULTS: SR T1-mapping showed <4 % deviation from the spin-echo reference in phantom in the range of T1 = 100-2300 ms. The average quality and artifact scores of the T1-mapping methods were MOLLI3.4/3.6, SAPPHIRE3.1/3.4, SASHA2.9/3.2; (1 poor - 4 excellent/1 strong - 4 none). SAPPHIRE and SASHA yielded significantly higher T1-times (SAPPHIRE 1578 ± 42 ms, SASHA 1523 ± 46 ms), in-vivo T1-time variation (SAPPHIRE 60.1 ± 8.7 ms, SASHA 70.0 ± 9.3 ms) and lower ECV-values (SAPPHIRE 0.20 ± 0.02, SASHA 0.21 ± 0.03) compared with MOLLI (T1 1181 ± 47 ms, ECV 0.26 ± 0.03, Precision 53.7 ± 8.1 ms). No significant difference was found in the inter-subject variability of T1-times or ECV-values (T1 p = 0.90, ECV p = 0.78), the observer agreement (inter p > 0.19; intra p > 0.09) or consistency (inter p > 0.07; intra p > 0.17) between the three methods. CONCLUSIONS: Saturation-recovery T1-mapping at 3T yields higher accuracy, comparable inter-subject, inter- and intra-observer variability and less than 30 % precision-loss compared to MOLLI.