Efficient T 2 mapping with blip‐up/down EPI and gSlider‐SMS

Abstract

Purpose To rapidly obtain high isotropic‐resolution T 2 maps with whole‐brain coverage and high geometric fidelity. Methods A T 2 blip‐up/down EPI acquisition with generalized slice‐dithered enhanced resolution (T 2 ‐BUDA‐gSlider) is proposed. A RF‐encoded multi‐slab spin‐echo (SE) EPI acquisition with multiple TEs was developed to obtain high SNR efficiency with reduced TR. This was combined with an interleaved 2‐shot EPI acquisition using blip‐up/down phase encoding. An estimated field map was incorporated into the joint multi‐shot EPI reconstruction with a structured low rank constraint to achieve distortion‐free and robust reconstruction for each slab without navigation. A Bloch simulated subspace model was integrated into gSlider reconstruction and used for T 2 quantification. Results In vivo results demonstrated that the T 2 values estimated by the proposed method were consistent with gold standard spin‐echo acquisition. Compared to the reference 3D fast spin echo (FSE) images, distortion caused by off‐resonance and eddy current effects were effectively mitigated. Conclusion BUDA‐gSlider SE‐EPI acquisition and gSlider‐subspace joint reconstruction enabled distortion‐free whole‐brain T 2 mapping in 2 min at ~1 mm 3 isotropic resolution, which could bring significant benefits to related clinical and neuroscience applications.