3D Simultaneous Post-Contrast T1/T2 Mapping and Synthetic Multi-Contrast Late Gadolinium Enhancement at 0.55T

Objectives: To propose and validate a simplified method for 3D simultaneous post-contrast parametric mapping and synthetic late gadolinium enhancement (LGE) imaging at 0.55T for comprehensive whole-heart myocardial tissue characterization. Materials and Methods: A 3D joint T1/T2 mapping research sequence is adopted from a previous study. Three interleaved volumes with inversion recovery (IR) preparation, no magnetization preparation, and T2 preparation were acquired with image navigators to enable 100% respiratory scan efficiency. Intrinsically co-registered 3D T1, T2, and proton density maps were calculated using a dictionary-matching method, and Bloch equation-based IR and T2 preparation-IR (T2IR) signal models were proposed to generate multi-contrast 3D synthetic LGE images. In vivo evaluation included 10 data sets from a porcine myocardial infarction model to validate the performance of the proposed 3D method in comparison with that of separately scanned 2D reference sequences including post-contrast T1 mapping, pre-contrast T2 mapping, and LGE. Results: For the 10 swine data sets, 2D and 3D T1/T2 maps had consistent findings regarding the changes in T1/T2 values of myocardial infarction, presenting significantly decreased post-contrast T1 (2D: 279±48 vs. 472±44 ms, P <0.01; 3D: 355±32 vs. 597±48 ms, P <0.01) and increased T2 (2D: 102.4±11.5 vs. 66.4±3.1 ms, P <0.01; 3D: 71.0±5.3 vs. 39.4±4.5 ms, P <0.01) in scar compared with remote myocardium. 3D multi-contrast LGE images were successfully generated without additional scan and provided excellent image contrasts. Compared with 2D LGE, 3D synthetic bright-blood IR-LGE had improved scar-to-myocardium contrast ( P <0.01) with comparable image contrasts of scar-to-blood ( P =0.08) and blood-to-myocardium ( P =0.71), synthetic gray-blood IR-LGE had improved scar-to-blood and scar-to-myocardium contrast ( P <0.01) with comparable blood-to-myocardium contrast ( P =0.06), whereas synthetic dark-blood T2IR-LGE demonstrated significant differences regarding all tissue contrasts ( P <0.01). Conclusions: The proposed method provided imaging findings consistent with 2D references and shows promise for comprehensive myocardial tissue characterization in a single simple scan.