Accelerated free-breathing whole-heart 3D T₂ mapping with high isotropic resolution

To enable free-breathing whole-heart 3D T₂ mapping with high isotropic resolution in a clinically feasible and predictable scan time. This 3D motion-corrected undersampled signal matched (MUST) T₂ map is achieved by combining an undersampled motion-compensated T₂ -prepared Cartesian acquisition with a high-order patch-based reconstruction.

The 3D MUST-T₂ mapping acquisition consists of an electrocardiogram-triggered, T₂ -prepared, balanced SSFP sequence with nonselective saturation pulses. Three undersampled T₂ -weighted volumes are acquired using a 3D Cartesian variable-density sampling with increasing T₂ 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 T₂ maps. The proposed framework was evaluated in simulations, phantom experiments, and in vivo (10 healthy subjects, 2 patients) with 1.5-mm³ isotropic resolution. Three-dimensional MUST-T₂ was compared against standard multi-echo spin-echo sequence (phantom) and conventional breath-held single-shot 2D SSFP T₂ mapping (in vivo).

Three-dimensional MUST-T₂ showed high accuracy in phantom experiments (R² > 0.99). The precision of T₂ values was similar for 3D MUST-T₂ and 2D balanced SSFP T₂ mapping in vivo (5 ± 1 ms versus 4 ± 2 ms, P = .52). Slightly longer T₂ values were observed with 3D MUST-T₂ in comparison to 2D balanced SSFP T₂ mapping (50.7 ± 2 ms versus 48.2 ± 1 ms, P < .05). Preliminary results in patients demonstrated T₂ values in agreement with literature values.

The proposed approach enables free-breathing whole-heart 3D T₂ mapping with high isotropic resolution in about 8 minutes, achieving accurate and precise T₂ quantification of myocardial tissue in a clinically feasible scan time.