Browsing by Author "De la Sotta, Rafael I."

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    Motion corrected 3D whole-heart SAVA T 1 mapping at 0.55 T.
    (2025) De la Sotta, Rafael I.; Crabb, Michael G.; Kunze, Karl P.; Botnar, René M.; Prieto, Claudia
    PURPOSE: To propose a novel highly efficient isotropic-resolution 3D whole-heart saturation-recovery and variable-flip-angle (SAVA) T 1 mapping sequence at 0.55 T, incorporating image navigator (iNAV)-based non-rigid motion correction and dictionary matching. METHODS: The proposed iNAV-based isotropic-resolution 3D whole-heart SAVA T 1 mapping sequence at 0.55 T acquires three gradient echo T 1-weighted volumes sequentially: an equilibrium contrast with 4° flip angle, and two saturation recovery T 1-weighted contrasts with 10° flip angles and different saturation delays. Sequence parameters were optimized for the lower field strength by simulations and phantom experiments. Two-dimensional iNAVs are acquired at each heartbeat to enable respiratory motion estimation and correction and 100% respiratory scan efficiency. The T 1 mapping is computed by dictionary matching, using subject-specific dictionaries based on Bloch equations simulations. Non-rigid motion correction is implemented based on respiratory bins reconstructed by iterative-SENSE and subsequent patch-based low-rank denoising, for each contrast separately. The proposed approach was evaluated in a standardized T 1 phantom and 10 healthy subjects, in comparison to spin-echo reference and 2D MOLLI, respectively. RESULTS: Excellent agreement is observed between iNAV-based SAVA T 1 mapping at 0.55 T and spin echo reference in phantom, with a R 2 = 0.998 $$ {R}^2=0.998 $$ for all phantom vials. Good image quality was obtained in vivo for the contrast images and corresponding T 1 maps in a scan time of 6:30 min ±40 s. Average and SD of myocardial T 1 values across subjects and segments was 706 ± 41 ms, which is comparable to acquired 2D MOLLI values of 681 ± 26 ms, and previously reported 2D MOLLI values of 701 ± 24 ms. Coefficient of variation values (12%) are higher than those previously reported for diaphragmatic navigator-based non-isotropic SAVA T 1 mapping at 3 T (7.4%). CONCLUSION: The proposed iNAV-based SAVA approach achieves free-breathing motion-corrected 3D whole-heart T 1 mapping at 0.55 T in approximately 7 min scan time for an isotropic resolution of 2 mm. In vivo experiments showed that the proposed sequence achieves good map quality, with comparable T 1 values and spatial variability compared to 2D MOLLI T 1 mapping. Further evaluation is warranted in patients with cardiovascular disease.