Native myocardial longitudinal (T1 ) relaxation time: Regional, age, and sex associations in the healthy adult heart.

PURPOSE: To use magnetic resonance imaging (MRI) at two field strengths to assess healthy adults' regional myocardial noncontrast (native) T1 relaxation time distribution, and global myocardial native T1 between sexes and across age groups. MATERIALS AND METHODS: In all, 84 healthy volunteers underwent MRI at 1.5T and 3.0T. T1 maps were acquired in three left ventricular short axis slices using an optimized modified Look-Locker inversion recovery investigational prototype sequence. T1 measurements in msec were calculated from 16 regions-of-interest, and a global T1 value from all evaluable segments per subject. Associations were assessed with a multivariate linear regression model. RESULTS: In total, 1297 (96.5%) segments were evaluable at 1.5T and 1263 (94.0%) segments at 3.0T. Native T1 was higher in septal than lateral myocardium (1.5T: 956.3 ± 44.4 vs. 939.2 ± 54.2 msec; P < 0.001; 3.0T: 1158.2 ± 45.9 vs. 1148.9 ± 56.9 msec; P = 0.012). Native T1 decreased with increasing age in females but not in males. Among lowest age tertile (<33 years) global native T1 was higher in females than in males at 1.5T (960.0 ± 20.3 vs. 931.5 ± 22.2 msec, respectively; P = 0.003) and 3.0T (1166.5 ± 19.7 vs. 1130.2 ± 20.6 msec; P < 0.001). No sex differences were observed in upper age tertile (≥55 years) at 1.5T (937.7 ± 25.4 vs. 934.7 ± 22.3 msec; P = 0.762) or 3.0T (1153.0 ± 30.0 vs. 1132.3 ± 23.5 msec; P = 0.056). Association of global native T1 to age (P = 0.002) and sex (P < 0.001) was independent of field strength and body size. CONCLUSION: In healthy adults, native T1 values are highest in the ventricular septum. Global native T1 was inversely associated with age in women, but not in men. J. Magn. Reson. Imaging 2016;44:541-548.