Cardiac magnetic resonance T2 mapping and T2* mapping for myocardial iron detection in iron-water phantom models and pediatric patients with transfusion-dependent thalassemia: a comparison study.

Abstract

Background: The cardiac magnetic resonance (CMR) T2* mapping technique is widely used to quantify myocardial iron and assess iron overload in patients with transfusion-dependent thalassemia (TDT). However, the value of T2 mapping in detecting iron overload and its consistency with T2* mapping in the myocardium of pediatric patients are unknown. Thus, this study sought to explore the utility and feasibility of using T2 mapping to assess iron overload, and to provide an alternative non-invasive method for the assessment of iron overload in clinical practice.

Methods: Vitro iron-water phantom models with different iron concentrations were used to analyze the correlation between the T2 and T2* values. In total, 113 TDT pediatric patients were prospectively enrolled in the study and underwent CMR examinations using a Philips 1.5T scanner, and T2 and T2* mapping of the short-axis of the left ventricle were performed. Pearson correlation analyses, Bland-Altman plots, the Student's t-test or Mann-Whitney U test, Receiver operating characteristic (ROC) curve analyses, and intraclass correlation coefficient (ICC) were applied to analyze the data.

Results: Excellent negative correlations were found between the actual iron concentration and the measured T2* (r=-0.919, P=0.003) and T2 values (r=-0.888, P=0.008) of the vitro iron-water phantom models. Additionally, the measured T2* and T2 values of the phantom models were positively correlated (r=0.997, P<0.001). Bland-Altman plots revealed that the T2* and T2 values showed good agreement at the basal, middle, and apical levels of the left ventricle short-axis. The areas under the ROC curves for the diagnosis of myocardial iron overload by T2 mapping in the basal, middle, and apical segments were 0.78, 0.95, and 0.89, respectively.

Conclusions: The T2 mapping technique may serve as an alternative and complementary method to the T2* mapping technique in assessing iron overload in TDT patients, which provides a new use of routine T2 mapping.