High Spatial Resolution and Temporally Resolved T2* Mapping of Normal Human Myocardium at 7.0 Tesla: An Ultrahigh Field Magnetic Resonance Feasibility Study

Myocardial tissue characterization using T 2 * relaxation mapping techniques is an emerging application of (pre)clinical cardiovascular magnetic resonance imaging. The increase in microscopic susceptibility at higher magnetic field strengths renders myocardial T 2 * mapping at ultrahigh magnetic fields conceptually appealing. This work demonstrates the feasibility of myocardial T 2 * imaging at 7.0 T and examines the applicability of temporally-resolved and high spatial resolution myocardial T 2 * mapping. In phantom experiments single cardiac phase and dynamic (CINE) gradient echo imaging techniques provided similar T 2 * maps. In vivo studies showed that the peak-to-peak B 0 difference following volume selective shimming was reduced to approximately 80 Hz for the four chamber view and mid-ventricular short axis view of the heart and to 65 Hz for the left ventricle. No severe susceptibility artifacts were detected in the septum and in the lateral wall for T 2 * weighting ranging from TE = 2.04 ms to TE = 10.2 ms. For TE >7 ms, a susceptibility weighting induced signal void was observed within the anterior and inferior myocardial segments. The longest T 2 * values were found for anterior (T 2 *  = 14.0 ms), anteroseptal (T 2 *  = 17.2 ms) and inferoseptal (T 2 *  = 16.5 ms) myocardial segments. Shorter T 2 * values were observed for inferior (T 2 *  = 10.6 ms) and inferolateral (T 2 *  = 11.4 ms) segments. A significant difference (p = 0.002) in T 2 * values was observed between end-diastole and end-systole with T 2 * changes of up to approximately 27% over the cardiac cycle which were pronounced in the septum. To conclude, these results underscore the challenges of myocardial T 2 * mapping at 7.0 T but demonstrate that these issues can be offset by using tailored shimming techniques and dedicated acquisition schemes.