3D Whole‐Heart Joint T 1 /T 1ρ Mapping and Water‐Fat Imaging on a Clinical 0.55‐T Low‐Field Scanner

ABSTRACT Myocardial maps are conventionally acquired in 2D breath‐hold single‐parameter scans that are slow and have limited heart coverage. To overcome limitations associated with 2D breath‐hold mapping sequences, we develop a novel free‐breathing 3D joint / mapping sequence with Dixon encoding to provide co‐registered 3D and maps and water‐fat volumes with isotropic spatial resolution in a single scan for comprehensive contrast‐agent free myocardial tissue characterization and visualisation of the whole‐heart anatomy on a clinical 0.55‐T MR scanner. The proposed sequence acquires four interleaved 3D volumes with preparation modules to provide and encoding, with data acquired with a two‐echo Dixon readout and 2D image navigators to enable respiratory scan efficiency. Images were reconstructed with nonrigid respiratory motion‐corrected iterative SENSE with multi‐dimensional low‐rank patch‐based denoising, and maps generated by matching with simulated dictionaries. The proposed sequence was tested in phantoms, 11 healthy subjects and 1 patient, and compared with conventional techniques. For phantoms, the proposed 3D and measurements showed good correlation with 2D spin‐echo reference measurements. For healthy subjects, septal myocardial tissue mapping values were and for the proposed sequence, against and for 2D modified Look‐Locker inversion recovery and 2D respectively. Promising results were obtained when the proposed mapping was compared to 2D late‐gadolinium enhancement imaging in a patient. The proposed approach enables simultaneous 3D whole‐heart joint / mapping and water‐fat imaging at 0.55 T in a single scan of min, demonstrating good agreement with conventional techniques in phantoms and healthy subjects, and promising results in a patient.