Normal values of native T₁ and T₂ relaxation times on 3T cardiac MR in a healthy pediatric population aged 9-18 years

Background: Native myocardial T₁ and T₂ relaxation times are diagnostic tools used in clinical practice for adult and pediatric populations. Use of a mapping technique requires accurate knowledge of normal ranges in healthy patients, which is lacking in pediatric populations.

Purpose: To establish normal values for native T₁ and T₂ mapping in healthy pediatric subjects of different ages and sex.

Study type: Prospective.

Population: Thirty-eight healthy children (9-18 years; mean age 14.0 ± 2.7).

Field strength: Cardiac MR with a 3T scanner. T₁ and T₂ mapping using MyoMaps software.

Assessment: T₁ and T₂ relaxation times were calculated from a 0.7-1.0 cm² region of interest placed at the mid-ventricular short-axis slice in the interventricular septum by two observers. Inter- and intraobserver variability was assessed.

Statistical tests: The Student's t-test or the Mann-Whitney test for unpaired samples was applied to compare one continuous variable between two category groups. One-way analysis of variance (ANOVA) or a Kruskal-Wallis test was applied to compare one continuous variable between three category groups. Correlation between two continuous variables was assessed with a Pearson or Spearman test.

Results: The mean native T₁ relaxation time was 1223 ± 29 msec and T₂ relaxation time was 43 ± 4.5 msec. There was no correlation between T₁ /T₂ values and age or body surface area (for T₁ P = 0.94 and 0.90 and for T₂ P = 0.19 and 0.64, respectively). There was weak correlation between T₁ values and body mass index (BMI) (r = 0.448, P = 0.005). T₂ values were significantly higher in females compared with males (44.6 ± 4.2 vs. 40.4 ± 3.8 msec, P = 0.002). We found a significant rise of T₂ relaxation time in the pubertal period (age 13-15 years) comparing to prepubertal (age 9-12 years). Inter- and intraobserver agreement of T₁ (r = 0.93; r = 0.99) and T₂ (r = 0.96; r = 0.95) were high.

Data conclusion: We report normal values of native T₁ and T₂ relaxation times obtained with Myomaps software for 3T cardiac MR in a healthy pediatric population.

Level of evidence: 2 Technical Efficacy: Stage 2 J. Magn. Reson. Imaging 2020;51:912-918.