Accelerated 3D Free-breathing High-resolution Myocardial T Mapping at 3 Tesla

Purpose: To develop a fast free-breathing whole-heart high-resolution myocardial T 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 preparation. Multiple T -weighted images were acquired with T 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 mapping technique was investigated in phantoms and in vivo in 10 healthy subjects compared with the 2D T mapping.

Results: The 3D T mapping technique provided similar phantom T measurements in the range of 25-120 ms to the 2D T 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 -weighted images and T maps were obtained. Myocardial T values with the 3D T mapping were slightly longer than 2D breath-hold measurements (septal T : 52.7 ± 1.4 ms vs. 50.2 ± 1.8 ms, P < 0.01).

Conclusion: A fast 3D free-breathing whole-heart T mapping technique was proposed for T quantification at 3 T with isotropic spatial resolution (2 mm ) and short scan time of ∼4.5 min.