title: Reference-free unwarping of single-shot spatiotemporally encoded MRI using asymmetric self-refocused echoes acquisition.
abstract: This paper presents a phase evolution rewinding algorithm for correcting the geometric and intensity distortions in single-shot spatiotemporally encoded (SPEN) MRI with acquisition of asymmetric self-refocused echo trains. Using the field map calculated from the phase distribution of the source image, the off-resonance induced phase errors are successfully rewound through deconvolution. The alias-free partial Fourier transform reconstruction helps improve the signal-to-noise ratio of the field maps and the output images. The effectiveness of the proposed algorithm was validated through 7 T MRI experiments on a lemon, a water phantom, and in vivo rat head. SPEN imaging was evaluated using rapid acquisition by sequential excitation and refocusing (RASER) which produces uniform T2 weighting. The results indicate that the new technique can more robustly deal with the cases in which the images obtained with conventional single-shot spin-echo EPI are difficult to be restored due to serious field variations.
authors.affiliation: Department of Electronic Science, Fijian Provincial Key Laboratory of Plasma and Magnetic Resonance, State Key Laboratory of Physical Chemistry of Solid Surfaces, Xiamen University, Xiamen, China; Center for Brain Imaging Science and Technology, Zhejiang University, Hangzhou, China.
authors.forename: Ying
authors.initials: Y
authors.lastname: Chen
authors.affiliation: Center for Brain Imaging Science and Technology, Zhejiang University, Hangzhou, China.
authors.forename: Song
authors.initials: S
authors.lastname: Chen
authors.affiliation: Center for Brain Imaging Science and Technology, Zhejiang University, Hangzhou, China. Electronic address: jzhong3@zju.edu.cn.
authors.forename: Jianhui
authors.initials: J
authors.lastname: Zhong
authors.affiliation: Department of Electronic Science, Fijian Provincial Key Laboratory of Plasma and Magnetic Resonance, State Key Laboratory of Physical Chemistry of Solid Surfaces, Xiamen University, Xiamen, China. Electronic address: chenz@xmu.edu.cn.
authors.forename: Zhong
authors.initials: Z
authors.lastname: Chen
mesh_terms: D000465:Algorithms; D000818:Animals; D002138:Calibration; D002957:Citrus / Q000033:anatomy & histology; D017352:Echo-Planar Imaging / Q000379:methods*; D005583:Fourier Analysis; D006257:Head / Q000033:anatomy & histology; D007091:Image Processing, Computer-Assisted; D019047:Phantoms, Imaging; D051381:Rats
keywords: Asymmetric spin-echo EPI; Dynamic MRI; EPI distortion correction; Field mapping; Phase evolution rewinding; Spatiotemporal encoding