Accelerated 3D free-breathing high-resolution myocardial T1ρ mapping at 3 Tesla

Purpose: To develop a fast free-breathing whole-heart high-resolution myocardial T-1 rho mapping technique with robust spin-lock preparation that can be performed at 3 Tesla. Methods: An adiabatically excited continuous-wave spin-lock module, insensitive to field inhomogeneities, was implemented with an electrocardiogram-triggered low-flip angle spoiled gradient echo sequence with variable-density 3D Cartesian undersampling at a 3 Tesla whole-body scanner. A saturation pulse was performed at the beginning of each cardiac cycle to null the magnetization before T-1 rho preparation. Multiple T-1 rho-weighted images were acquired with T-1 rho preparations with different spin-lock times in an interleaved fashion. Respiratory self-gating approach was adopted along with localized autofocus to enable 3D translational motion correction of the data acquired in each heartbeat. After motion correction, multi-contrast locally low-rank reconstruction was performed to reduce undersampling artifacts. The accuracy and feasibility of the 3D T-1 rho mapping technique was investigated in phantoms and in vivo in 10 healthy subjects compared with the 2D T-1 rho mapping. Results: The 3D T-1 rho mapping technique provided similar phantom T-1 rho measurements in the range of 25-120 ms to the 2D T-1 rho mapping reference over a wide range of simulated heart rates. With the robust adiabatically excited continuous-wave spin-lock preparation, good quality 2D and 3D in vivo T-1 rho-weighted images and T-1 rho maps were obtained. Myocardial T-1 rho values with the 3D T-1 rho mapping were slightly longer than 2D breath-hold measurements (septal T-1 rho: 52.7 +/- 1.4 ms vs. 50.2 +/- 1.8 ms, P < 0.01). Conclusion: A fast 3D free-breathing whole-heart T-1 rho mapping technique was proposed for T-1 rho quantification at 3 T with isotropic spatial resolution (2 mm(3)) and short scan time of similar to 4.5 min.