3D Whole-Heart Joint T1/T1ρ Mapping and Water-Fat Imaging on a Clinical 0.55-T Low-Field Scanner.

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 $$ {T}_1 $$ / T 1 ρ $$ {T}_{1\rho } $$ mapping sequence with Dixon encoding to provide co-registered 3D T 1 $$ {T}_1 $$ and T 1 ρ $$ {T}_{1\rho } $$ 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 $$ {T}_1 $$ and T 1 ρ $$ {T}_{1\rho } $$ encoding, with data acquired with a two-echo Dixon readout and 2D image navigators to enable 100 % $$ 100\% $$ 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 $$ {T}_1 $$ and T 1 ρ $$ {T}_{1\rho } $$ measurements showed good correlation with 2D spin-echo reference measurements. For healthy subjects, septal myocardial tissue mapping values were T 1 = 743 ± 19 ms $$ {T}_1=743\pm 19\kern0.3em \mathrm{ms} $$ and T 1 ρ = 46 . 9 ± 2 . 7 ms $$ {T}_{1\rho }=46.9\pm 2.7\kern0.3em \mathrm{ms} $$ for the proposed sequence, against T 1 = 681 ± 23 ms $$ {T}_1=681\pm 23\kern0.3em \mathrm{ms} $$ and T 1 ρ = 57 . 9 ± 3 . 6 ms $$ {T}_{1\rho }=57.9\pm 3.6\kern0.3em \mathrm{ms} $$ for 2D modified Look-Locker inversion recovery and 2D T 1 ρ $$ {T}_{1\rho } $$ 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 $$ {T}_1 $$ / T 1 ρ $$ {T}_{1\rho } $$ mapping and water-fat imaging at 0.55 T in a single scan of ≈ 11 $$ \approx 11 $$ min, demonstrating good agreement with conventional techniques in phantoms and healthy subjects, and promising results in a patient.