Normal Values of Magnetic Resonance T1ρ Relaxation Times in the Adult Heart at 1.5 T MRI.

BACKGROUND: T1ρ mapping is a new quantitative MRI technique in recent years. In order to use T1ρ 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 T1ρ values in healthy adults and to explore the influence of slice location and gender on T1ρ 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) (T1 mapping), multiecho gradient-spin-echo (GraSE) (T2 mapping) and T1ρ -prepared steady-state free precession (T1ρ mapping) sequences. ASSESSMENT: Basal, mid, and apical short-axis left ventricular T1 , T2 , and T1ρ maps were acquired. T1ρ maps at spin-locking frequencies of 5 and 400 Hz were subtracted to create myocardial fibrosis index (mFI) maps. Slice-average and global average T1 , T2 , T1ρ , 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 , T1ρ, and mFI were 1053 ± 34 msec, 51.9 ± 2.3 msec, 47.9 ± 2.8 msec, and 4.4 ± 1.6 msec. T1ρ 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 T1ρ 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, respectively). In addition, there was a moderate positive correlation between global T1ρ values and global T1 values (r = 0.44, P < 0.05) and a moderate positive correlation between global T1ρ values and global T2 values (r = 0.42, P < 0.05). DATA CONCLUSION: In this study, the global T1ρ values of healthy adults' hearts were 47.9 ± 2.8 msec. This study found that gender and slice location of myocardium can affect the T1ρ values. EVIDENCE LEVEL: 4 TECHNICAL EFFICACY: Stage 1.