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

To develop a cardiac T mapping method for free-breathing 3D T mapping of the whole heart at 3 T with transmit B ( ) correction. A free-breathing, electrocardiogram-gated inversion-recovery sequence with spoiled gradient-echo readout was developed and optimized for cardiac T 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 and flip-angle estimation was performed in T mapping to improve its robustness to inhomogeneity. Subject-specific timing of data acquisition was used in the estimation to account for natural heart-rate variations during the imaging experiment. Simulations showed that accuracy and precision of T mapping can be improved with joint T 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 maps from the proposed method and the reference method. Three-dimensional cardiac T 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 values comparable to those obtained from modified Look-Locker inversion recovery. The proposed method generated 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. The proposed method allows free-breathing 3D T mapping of the whole heart with transmit B correction in a practical imaging time.