Native myocardial longitudinal (T (1)) 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) T (1) relaxation time distribution, and global myocardial native T (1) between sexes and across age groups. MATERIALS AND METHODS: In all, 84 healthy volunteers underwent MRI at 1.5T and 3.0T. T (1) maps were acquired in three left ventricular short axis slices using an optimized modified Look–Locker inversion recovery investigational prototype sequence. T (1) measurements in msec were calculated from 16 regions‐of‐interest, and a global T (1) 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 T (1) 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 T (1) decreased with increasing age in females but not in males. Among lowest age tertile (<33 years) global native T (1) 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 T (1) to age (P = 0.002) and sex (P < 0.001) was independent of field strength and body size. CONCLUSION: In healthy adults, native T (1) values are highest in the ventricular septum. Global native T (1) was inversely associated with age in women, but not in men. J. Magn. Reson. Imaging 2016;44:541–548.