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Center‐out EPI (COEPI): A fast single‐shot imaging technique with a short TE
Author(s) -
Chen Xudong,
Zhu Ante,
Du Yiping P.
Publication year - 2020
Publication title -
magnetic resonance in medicine
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.696
H-Index - 225
eISSN - 1522-2594
pISSN - 0740-3194
DOI - 10.1002/mrm.28175
Subject(s) - single shot , physics , nuclear magnetic resonance , spin echo , nuclear medicine , k space , echo planar imaging , fast spin echo , magnetic resonance imaging , waveform , optics , fourier transform , medicine , radiology , quantum mechanics , voltage
Purpose To develop a center‐out echo planar imaging (COEPI) acquisition technique to increase SNR through minimizing the TE. Methods In single‐shot COEPI, the phase‐encoding starts from the center ( k y = 0) toward both sides of k‐space to substantially shorten the TE compared to the conventional single‐shot EPI. The phase‐encoding gradient waveform is partially overlapped with the frequency‐encoding gradient waveform to keep the echo spacing constant during the echo train readout. A reconstruction pipeline was developed to correct for phase and off‐resonance errors in COEPI. Gradient‐recalled echo (GRE), spin echo (SE), and DWI COEPI were obtained in phantoms and healthy brains at 1.5 tesla (T) and 3.0T. The SNR in COEPI and single‐shot partial k y EPI was compared. Results Acquisition matrix of 128 × 80 (16 overscan lines) was obtained in both COEPI and EPI. At 1.5T/3.0T, a minimum TE of 3 ms/4 ms in GRE‐COEPI, 11 ms/12 ms in SE‐COEPI, and 40 ms in DWI‐COEPI (3.0T only, maximum b value = 2000 s/mm 2 ) was achieved, compared to a minimum TE of 18 ms/16 ms in GRE‐EPI, 37 ms/34 ms in SE‐EPI, and 66 ms in DWI‐EPI, respectively. Image blurring and Nyquist ghost appear in COEPI and were substantially reduced after corrections. At 1.5T/3.0T, a SNR increase of 27.7% ± 6.9%/20.7% ± 7.0% in GRE‐COEPI and 37.7% ± 5.7%/28.2% ± 1.3% in SE‐COEPI was observed in white matter of human brains, compared to GRE‐EPI and SE‐EPI, respectively. At 3.0T, a SNR increase of 41.2% ± 4.1% in DWI‐COEPI was observed in white matter of 5 subjects at 5 b values (0~2000 s/mm 2 ), compared to DWI‐EPI. Conclusion The feasibility of COEPI and its SNR benefit were demonstrated in this study.