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

Background T 1 ρ mapping is a new quantitative MRI technique in recent years. In order to use T 1 ρ 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 ρ values in healthy adults and to explore the influence of slice location and gender on T 1 ρ 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 T 1 ρ ‐prepared steady‐state free precession (T 1 ρ mapping) sequences. Assessment Basal, mid, and apical short‐axis left ventricular T 1 , T 2 , and T 1 ρ maps were acquired. T 1 ρ maps at spin‐locking frequencies of 5 and 400 Hz were subtracted to create myocardial fibrosis index (mFI) maps. Slice‐average and global average T 1 , T 2 , T 1 ρ , 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 T 1 , T 2 , T 1 ρ , and mFI were 1053 ± 34 msec, 51.9 ± 2.3 msec, 47.9 ± 2.8 msec, and 4.4 ± 1.6 msec. T 1 ρ 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 ρ 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 T 1 ρ values and global T 1 values ( r = 0.44, P < 0.05) and a moderate positive correlation between global T 1 ρ values and global T 2 values ( r = 0.42, P < 0.05). Data Conclusion In this study, the global T 1ρ 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 ρ values. Evidence Level 4 Technical Efficacy Stage 1