Free-breathing T2* mapping for MR myocardial iron assessment at 3 T.

BACKGROUND: Timely diagnosis of cardiac iron overload is important for children with transfusion-dependent anaemias and requires modern measure methods. Nowadays, myocardial iron quantification is performed by magnetic resonance (MR) breath-hold techniques, sensitive to respiratory motion and unfeasible in patients who are unable to hold their breath. Free-breathing T2* mapping sequences would allow to scan children who cannot hold their breath for a specified duration. Our aim was to test a free-breathing T2* mapping sequence, based on motion correction by multiple signal accumulation technique. METHODS: We used an electrocardiographically gated T2* mapping sequence based on multiple gradient echo at 3-T in 37 paediatric patients with haematologic disorders aged from 2 to 16. We compared T2* values of myocardium and signal-to-noise ratio of this new sequence with standard breath-holding T2* mapping sequence. T2* values were measured in the interventricular septum for both methods in studies with adequate image quality. RESULTS: All children were scanned without complications. Five patients were excluded from analysis because of the presence of respiratory artefacts on the T2* images with breath-holding technique due to patient's inability to hold their breath. Breath-holding T2* was 19.5 +/- 7.7 ms (mean +/- standard deviation), free-breathing T2* was 19.4 +/- 7.6 ms, with positive correlation (r = 0.99, R(2) = 0.98; p < 0.001). The free-breathing sequence had a higher signal-to-noise ratio (median 212.8, interquartile range 148.5-566.5) than the breath-holding sequence (112.6, 71.1-334.1) (p = 0.03). CONCLUSION: A free-breathing sequence provided accurate measurement of myocardial T2* values in children.