Accelerated free‐breathing whole‐heart 3D T(2) mapping with high isotropic resolution

PURPOSE: To enable free‐breathing whole‐heart 3D T(2) mapping with high isotropic resolution in a clinically feasible and predictable scan time. This 3D motion‐corrected undersampled signal matched (MUST) T(2) map is achieved by combining an undersampled motion‐compensated T(2)‐prepared Cartesian acquisition with a high‐order patch‐based reconstruction. METHODS: The 3D MUST‐T(2) mapping acquisition consists of an electrocardiogram‐triggered, T(2)‐prepared, balanced SSFP sequence with nonselective saturation pulses. Three undersampled T(2)‐weighted volumes are acquired using a 3D Cartesian variable‐density sampling with increasing T(2) preparation times. A 2D image‐based navigator is used to correct for respiratory motion of the heart and allow 100% scan efficiency. Multicontrast high‐dimensionality undersampled patch‐based reconstruction is used in concert with dictionary matching to generate 3D T(2) maps. The proposed framework was evaluated in simulations, phantom experiments, and in vivo (10 healthy subjects, 2 patients) with 1.5‐mm(3) isotropic resolution. Three‐dimensional MUST‐T(2) was compared against standard multi‐echo spin‐echo sequence (phantom) and conventional breath‐held single‐shot 2D SSFP T(2) mapping (in vivo). RESULTS: Three‐dimensional MUST‐T(2) showed high accuracy in phantom experiments (R(2) > 0.99). The precision of T(2) values was similar for 3D MUST‐T(2) and 2D balanced SSFP T(2) mapping in vivo (5 ± 1 ms versus 4 ± 2 ms, P = .52). Slightly longer T(2) values were observed with 3D MUST‐T(2) in comparison to 2D balanced SSFP T(2) mapping (50.7 ± 2 ms versus 48.2 ± 1 ms, P < .05). Preliminary results in patients demonstrated T(2) values in agreement with literature values. CONCLUSION: The proposed approach enables free‐breathing whole‐heart 3D T(2) mapping with high isotropic resolution in about 8 minutes, achieving accurate and precise T(2) quantification of myocardial tissue in a clinically feasible scan time.