3D Whole-Heart Joint T1/T1? 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 T-1/T-1 rho mapping sequence with Dixon encoding to provide co-registered 3D T-1 and T-1 rho 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 T-1 and T-1 rho encoding, with data acquired with a two-echo Dixon readout and 2D image navigators to enable 100% 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 T-1 and T-1 rho measurements showed good correlation with 2D spin-echo reference measurements. For healthy subjects, septal myocardial tissue mapping values were T-1 = 743 +/- 19 ms and T-1 rho = 46.9 +/- 2. 7 ms for the proposed sequence, against T-1 = 681 +/- 23 ms and T-1 rho = 57.9 +/- 3.6 ms for 2D modified Look-Locker inversion recovery and 2D T-1 rho 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 T-1/T-1 rho mapping and water-fat imaging at 0.55 T in a single scan of approximate to 11 min, demonstrating good agreement with conventional techniques in phantoms and healthy subjects, and promising results in a patient.