Reproducibility of three different cardiac T₂‐mapping sequences at 1.5T

Purpose To elucidate the impact of technical and intraindividual reproducibility on the overall variability of myocardial T 2 relaxation times. Materials and Methods Thirty healthy volunteers were examined three times (day 1 morning/evening, evening after 2–3 weeks) at 1.5T. During each examination three different T 2 ‐mapping sequences were acquired twice at three slices in short axis view: multi‐echo‐spin‐echo (MESE), T 2 ‐prepared balanced steady‐state free precession (SSFP) ( T 2 prep), and gradient‐spin‐echo with and without fat saturation (GraSE/GraSE FS ). Repeated measurements were performed for T 2 prep and GraSE. Segmented T 2 ‐maps were generated for each slice according to the American Heart Association (AHA) 16‐segment model. Results The coefficients of variation and intraclass correlation coefficients for intraobserver variability were: 1.3% and 0.89 for T 2 prep, 1.5% and 0.93 for GraSE, 3.1% and 0.83 for MESE; and for interobserver variability: 3.3% and 0.66 for T 2 prep, 2.0% and 0.83 for GraSE, 3.6% and 0.77 for MESE. No systematic difference of T 2 times was observed due to diurnal effects and on long‐term analysis using one‐way analysis of variance (ANOVA) with Tukey‐type multiple comparisons (morning vs. evening scan for T 2 prep: 52.5 ± 2.4 vs. 51.7 ± 2.7 msec, P = 0.119; for GraSE: 58.6 ± 4.0 vs. 58.5 ± 3.8 msec, P = 0.984; for GraSE FS 57.1 ± 3.2 vs. 57.2 ± 3.9 msec, P = 0.998, and for MESE: 53.8 ± 2.7 vs. 53.3 ± 3.3 msec, P = 0.541; scans between weeks for T 2 prep: 51.7 ± 2.7 vs. 51.4 ± 2.4 msec, P = 0.873; for GraSE: 58.5 ± 3.8 vs. 58.1 ± 3.4 msec, P = 0.736; for GraSE FS : 57.2 ± 3.9 vs. 57.0 ± 4.6 msec, P = 0.964, and for MESE: 53.3 ± 3.3 vs. 53.4 ± 2.4 msec, P = 0.970). ANOVA components, however, demonstrated a greater variance of T 2 times over multiple timepoints than for repeated measurements within the same scan (variance components of the model fit for intraday variance vs. repeated measurements: T 2 prep 2.22 vs. 1.36, GraSE 3.76 vs. 2.09, GraSE FS 3.96 vs. 1.58, MESE 1.86; and for interweeks variance vs. repeated measurements: T 2 prep 2.21 vs. 0.80, GraSE 3.20 vs. 2.10, GraSE FS 8.82 vs. 1.18, and MESE 4.49). Conclusion Technical reproducibility and intra‐ and interobserver agreement of myocardial T 2 relaxation times are excellent and intraindividual variation over time is small. Therefore, we consider subject‐related factors to explain most of the interindividual variability of myocardial T 2 times reported in previous studies. The acknowledgment of this subject‐related, biological variability may be important for the future diagnostic value of T 2 ‐mapping. J. Magn. Reson. Imaging 2016;44:1168–1178.