Normal Values of Magnetic Resonance T-1 rho Relaxation Times in the Adult Heart at 1.5 T MRI

Background: T1P mapping is a new quantitative MRI technique in recent years. In order to use T-1 rho mapping as a noncontrast method to assess myocardial fibrosis, it is necessary to establish a range of normal values. Purpose: To establish a potential normal range of cardiac T-1 rho values in healthy adults and to explore the influence of slice location and gender on T-1 rho values. Study Type: Prospective. Population: A total of 57 healthy volunteers without cardiovascular risk factors (age 26.7 +/- 11.8 years; 29 males). Field Strength/Sequence: 1.5 T; modified Look-Locker inversion recovery (MOLLI) (T-1 mapping), multiecho gradient-spin-echo (GraSE) (T-2 mapping) and T1P-prepared steady-state free precession (T-1 rho mapping) sequences. Assessment: Basal, mid, and apical short-axis left ventricular T-1 , T-2 , and T-1 rho maps were acquired. T-1 rho maps at spin-locking frequencies of 5 and 400 Hz were subtracted to create myocardial fibrosis index (mFI) maps. Slice-average and global aver-age T-1 , T-2 , T-1 rho , and mFI values were determined. Statistical Tests: Shapiro-Wilk test, Independent t-test, ANOVA test, Pearson correlation coefficient (r). Significance: P value < 0.05. Results: The global average values of T1 , T2 , T-1 rho, and mFI were 1053 +/- 34 msec, 51.9 +/- 2.3 msec, 47.9 +/- 2.8 msec, and 4.4 +/- 1.6 msec. T-1 rho values showed a significant gradual increase from the basal slice to the apical slice of the heart (basal 46.5 +/- 2.7 msec, mid 48.0 +/- 2.9 msec, apical 49.2 +/- 3.3 msec). The T-1 rho and mFI values of females (49.7 +/- 2.4 msec and 5.1 +/- 1.2 msec, respectively) were significantly higher than those of males (46.2 +/- 1.9 msec and 3.7 +/- 1.7 msec, respec-tively). In addition, there was a moderate positive correlation between global T-1 rho values and global T-1 values (r = 0.44, P < 0.05) and a moderate positive correlation between global T-1 rho values and global T-2 values (r = 0.42, P < 0.05). Data Conclusion: In this study, the global T-1 rho values of healthy adults' hearts were 47.9 +/- 2.8 msec. This study found that gender and slice location of myocardium can affect the T-1 rho values.