PURPOSE

To develop and validate a highly efficient motion compensated free-breathing isotropic resolution 3D whole-heart joint T/T mapping sequence with anatomical water/fat imaging at 0.55 T.

METHODS

The proposed sequence takes advantage of shorter T at 0.55 T to acquire three interleaved water/fat volumes with inversion-recovery preparation, no preparation, and T preparation, respectively. Image navigators were used to facilitate nonrigid motion-compensated image reconstruction. T and T maps were jointly calculated by a dictionary matching method. Validations were performed with simulation, phantom, and in vivo experiments on 10 healthy volunteers and 1 patient. The performance of the proposed sequence was compared with conventional 2D mapping sequences including modified Look-Locker inversion recovery and T-prepared balanced steady-SSFP sequence.

RESULTS

The proposed sequence has a good T and T encoding sensitivity in simulation, and excellent agreement with spin-echo reference T and T values was observed in a standardized T/T phantom (R = 0.99). In vivo experiments provided good-quality co-registered 3D whole-heart T and T maps with 2-mm isotropic resolution in a short scan time of about 7 min. For healthy volunteers, left-ventricle T mean and SD measured by the proposed sequence were both comparable with those of modified Look-Locker inversion recovery (640 ± 35 vs. 630 ± 25 ms [p = 0.44] and 49.9 ± 9.3 vs. 54.4 ± 20.5 ms [p = 0.42]), whereas left-ventricle T mean and SD measured by the proposed sequence were both slightly lower than those of T-prepared balanced SSFP (53.8 ± 5.5 vs. 58.6 ± 3.3 ms [p < 0.01] and 5.2 ± 0.9 vs. 6.1 ± 0.8 ms [p = 0.03]). Myocardial T and T in the patient measured by the proposed sequence were in good agreement with conventional 2D sequences and late gadolinium enhancement.

CONCLUSION

The proposed sequence simultaneously acquires 3D whole-heart T and T mapping with anatomical water/fat imaging at 0.55 T in a fast and efficient 7-min scan. Further investigation in patients with cardiovascular disease is now warranted.