Optimized AIR and investigational MOLLI cardiac T1 mapping pulse sequences produce similar intra-scan repeatability in patients at 3T

This study was conducted to improve the precision of arrhythmia-insensitive rapid (AIR) cardiac T-1 mapping through pulse sequence optimization and then evaluate the intra-scan repeatability in patients at 3T against investigational modified Look-Locker inversion recovery (MOLLI) T-1 mapping. In the first development phase (five human subjects), we implemented and tested centric-pair k-space ordering to suppress image artifacts associated with eddy currents. In the second development phase (15 human subjects), we determined optimal flip angles to reduce the measurement variation in T-1 maps. In the validation phase (35 patients), we compared the intra-scan repeatability between investigational MOLLI and optimized AIR. In 23 cardiac planes, conventional centric k-space ordering (3.7%) produced significantly (p < 0.05) more outliers as a fraction of left ventricular cavity area than optimal centric k-space ordering (1.4%). In 15 human subjects, for each of four types of measurement (native myocardial T-1, native blood T-1, post-contrast myocardial T-1, post-contrast blood T-1), flip angles of 55-65 degrees produced lower measurement variation while producing results that are not significantly different from those produced with the previously used flip angle of 35 degrees (p > 0.89, intra-class correlation coefficient >= 0.95 for all four measurement types). Compared with investigational MOLLI (coefficient of repeatability, CR = 40.0, 77.2, 26.5, and 25.9 ms for native myocardial, native blood, post-contrast myocardial, and post-contrast blood T-1, and 2.0% for extracellular volume (ECV) measurements, respectively), optimized AIR (CR = 54.3, 89.7, 30.5, and 14.7 ms for native myocardial, native blood, post-contrast myocardial, and post-contrast blood T-1, and 1.6% for ECV measurements, respectively) produced similar absolute intra-scan repeatability in all 35 patients in the validation phase. High repeatability is critically important for longitudinal studies, where the goal is to monitor physiologic/pathologic changes, not measurement variation. Optimized AIR cardiac T-1 mapping is likely to yield high scan-retest repeatability for pre-clinical and clinical applications.