Accelerated 3D echo‐planar spectroscopic imaging at 4 Tesla using modified blipped phase‐encoding

Whole‐brain echo‐planar spectroscopic imaging (EPSI) often substantially lengthens MRI/MRSI (magnetic resonance spectroscopic imaging) protocols. To halve acquisition time, application of a blipped phase‐encoding (PE) gradient during the EPSI readout (RO) was previously suggested by PE of the even RO echoes in k ‐space at an interstitial location along k PE , separated from the odd RO echoes, effectively reducing the number of PEs by a factor of 2. However, the approach is very susceptible to phase inconsistencies between even and odd RO echoes in the presence of B 0 inhomogeneities and gradient imbalance, leading to ghosting in the PE direction. In this work, the blipped PE gradient is placed in between pairs of even/odd RO gradient lobes to avoid these problems. This approach is demonstrated in a phantom and in normal human brain in vivo at 4T. While the proposed method allows substantial reduction in metabolite ghosting, it may be limited by the presence of a relatively large spurious signal at the Nyquist frequency. Magn Reson Med 58:1061–1066, 2007. © 2007 Wiley‐Liss, Inc.