Comparison of Three Different Cardiac T2-Mapping Techniques at 1.5 Tesla

Abstract

Background: T2-mapping techniques gain increasing acceptance to study myocardial edema in inflammatory and ischemic heart diseases. Study Aim: To compare the performance of a breath-hold and two free-breathing T2-mapping techniques in a prospective design in healthy subjects. Methods: Three different sequences for T2-mapping were tested on a clinical CMR scanner (Aera, Siemens, Germany) at 1.5T: a) Breath-hold 2D-acquisition technique (2D-BH) b) Free-breathing 2D-technique applying a diaphragmatic navigator (2D-FBNav), and c) Free-breathing 3D-technique applying self-navigation for respiratory motion correction (3D-FBSN). T2-values were quantified in 6 segments per short-axis slice on 5 slices (2D-BH and 3D-FBSN) and 3 slices (2D-FBNav) covering the left ventricle. Analyses were also performed with larger segments (8- and 2-segment models). As a quality measure, the coefficient of variation (CV%=standard deviation of T2-value expressed as percentage of mean T2) was determined. Contours were drawn manually by 2 observers using commercial software (Gyrotools, Zurich, Switzerland). T2 differences between techniques, slices, and segments were evaluated by repeated-measures ANOVA and post-hoc Bonferroni-correction. Results: With 2D-BH, diagnostic images were obtained in all 13 volunteers (=390 segments). With 2D-FBNav 3 slices/volunteer were acquired and quality was non-diagnostic in 5 slices yielding 204 segments for analysis. With 3D-FBSN 1 volunteer was not evaluable yielding 360 segments for analysis. Mean T2-values (=T2 averaged over all segments) were higher for the 3D-FBSN (54.4±5.4ms vs. 48.5±2.4ms and 45.9±4.4ms for 2D-BH and 2D-FBNav, respectively, p<0.002). The CV% of the 3D-FBSN technique was higher vs. both, 2D-BH and 2D-FBNav (12.1±5.4% vs. 7.0±1.1% and 8.3±3.9%, respectively, p<0.02). Conclusion: At 1.5T, most reliable T2 results with a low coefficient of variation were obtained by the 2D-BH technique. The 2D-FBNav technique is considered as an alternative if breath-holding capacity is not sufficient. The 3D-FBSN technique is not at the same level of robustness as the breath-holding technique and not yet recommended for clinical use.