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.