Free‐breathing 3D whole‐heart joint T1/T2 mapping and water/fat imaging at 0.55 T

Abstract

AbstractPurposeTo develop and validate a highly efficient motion compensated free‐breathing isotropic resolution 3D whole‐heart joint T1/T2 mapping sequence with anatomical water/fat imaging at 0.55 T.MethodsThe proposed sequence takes advantage of shorter T1 at 0.55 T to acquire three interleaved water/fat volumes with inversion‐recovery preparation, no preparation, and T2 preparation, respectively. Image navigators were used to facilitate nonrigid motion‐compensated image reconstruction. T1 and T2 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 T2‐prepared balanced steady‐SSFP sequence.ResultsThe proposed sequence has a good T1 and T2 encoding sensitivity in simulation, and excellent agreement with spin‐echo reference T1 and T2 values was observed in a standardized T1/T2 phantom (R2 = 0.99). In vivo experiments provided good‐quality co‐registered 3D whole‐heart T1 and T2 maps with 2‐mm isotropic resolution in a short scan time of about 7 min. For healthy volunteers, left‐ventricle T1 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 T2 mean and SD measured by the proposed sequence were both slightly lower than those of T2‐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 T1 and T2 in the patient measured by the proposed sequence were in good agreement with conventional 2D sequences and late gadolinium enhancement.ConclusionThe proposed sequence simultaneously acquires 3D whole‐heart T1 and T2 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.