Free-breathing 3D cardiac T-1 mapping with transmit B-1 correction at 3T

Purpose To develop a cardiac T-1 mapping method for free-breathing 3D T-1 mapping of the whole heart at 3 T with transmit B-1 (B1+) correction. Methods A free-breathing, electrocardiogram-gated inversion-recovery sequence with spoiled gradient-echo readout was developed and optimized for cardiac T-1 mapping at 3 T. High-frame-rate dynamic images were reconstructed from sparse (k,t)-space data acquired along a stack-of-stars trajectory using a subspace-based method for accelerated imaging. Joint T-1 and flip-angle estimation was performed in T-1 mapping to improve its robustness to B1+ inhomogeneity. Subject-specific timing of data acquisition was used in the estimation to account for natural heart-rate variations during the imaging experiment. Results Simulations showed that accuracy and precision of T-1 mapping can be improved with joint T-1 and flip-angle estimation and optimized electrocardiogram-gated spoiled gradient echo-based inversion-recovery acquisition scheme. The phantom study showed good agreement between the T-1 maps from the proposed method and the reference method. Three-dimensional cardiac T-1 maps (40 slices) were obtained at a 1.9-mm in-plane and 4.5-mm through-plane spatial resolution from healthy subjects (n = 6) with an average imaging time of 14.2 +/- 1.6 minutes (heartbeat rate: 64.2 +/- 7.1 bpm), showing myocardial T-1 values comparable to those obtained from modified Look-Locker inversion recovery. The proposed method generated B1+ maps with spatially smooth variation showing 21%-32% and 11%-15% variations across the septal-lateral and inferior-anterior regions of the myocardium in the left ventricle. Conclusion The proposed method allows free-breathing 3D T-1 mapping of the whole heart with transmit B-1 correction in a practical imaging time.