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Echo planar time-resolved imaging (EPTI)
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DOI：10.1002/mrm.27673.png)
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Abstract
En 中文
Purpose: To develop an efficient distortion- and blurring-free multi-shot EPI technique for time-resolved multiple-contrast and/or quantitative imaging. Methods: EPI is a commonly used sequence but suffers from geometric distortions and blurring. Here, we introduce a new multi-shot EPI technique termed echo planar time-resolved imaging (EPTI), which has the ability to rapidly acquire distortion- and blurring-free multi-contrast data set. The EPTI approach performs encoding in k(y)-t space and uses a new highly accelerated spatio-temporal CAIPI sampling trajectory to take advantage of signal correlation along these dimensions. Through this acquisition and a B-0-informed parallel imaging reconstruction, hundreds of time-resolved distortion- and blurring-free images at different TEs across the EPI readout window can be created at sub-millisecond temporal increments using a small number of EPTI shots. Moreover, a method for self-estimation and correction of shot-to-shot B-0 variations was developed. Simultaneous multi-slice acquisition was also incorporated to further improve the acquisition efficiency. Results: We evaluated EPTI under varying simulated acceleration factors, B-0-inhomogeneity, and shot-to-shot B-0 variations to demonstrate its ability to provide distortion- and blurring-free images at multiple TEs. Two variants of EPTI were demonstrated in vivo at 3T: (1) a combined gradient- and spin-echo EPTI for quantitative mapping of T-2, T-2(*), proton density, and susceptibility at 1.1 X 1.1 X 3 mm(3) whole-brain in 28 s (0.8 s/slice), and (2) a gradient-echo EPTI, for multi-echo and quantitative T-2(*) fMRI at 2 X 2 X 3 mm(3) whole-brain at a 3.3 s temporal resolution. Conclusion: EPTI is a new approach for multi-contrast and/or quantitative imaging that can provide fast acquisition of distortion- and blurring-free images at multiple TEs.
Keywords:
distortion-free
EPI
fMRI
multi-contrast
quantitative imaging
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