Accelerated free-breathing whole-heart 3D T2 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.