Free‐breathing <scp>3D</scp> whole‐heart joint <scp>T<sub>1</sub></scp>/<scp>T<sub>2</sub></scp> mapping and water/fat imaging at 0.<scp>55 T</scp>
Dongyue Si, Michael Crabb, Karl Kunze, Simon Littlewood, Claudia Prieto, René M. Botnar
Abstract
Abstract Purpose To develop and validate a highly efficient motion compensated free‐breathing isotropic resolution 3D whole‐heart joint T 1 /T 2 mapping sequence with anatomical water/fat imaging at 0.55 T. Methods The proposed sequence takes advantage of shorter T 1 at 0.55 T to acquire three interleaved water/fat volumes with inversion‐recovery preparation, no preparation, and T 2 preparation, respectively. Image navigators were used to facilitate nonrigid motion‐compensated image reconstruction. T 1 and T 2 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 2 ‐prepared balanced steady‐SSFP sequence. Results The proposed sequence has a good T 1 and T 2 encoding sensitivity in simulation, and excellent agreement with spin‐echo reference T 1 and T 2 values was observed in a standardized T 1 /T 2 phantom ( R 2 = 0.99). In vivo experiments provided good‐quality co‐registered 3D whole‐heart T 1 and T 2 maps with 2‐mm isotropic resolution in a short scan time of about 7 min. For healthy volunteers, left‐ventricle T 1 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 2 mean and SD measured by the proposed sequence were both slightly lower than those of T 2 ‐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 1 and T 2 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 1 and T 2 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.