Accelerated 3D echo-planar spectroscopic imaging at 4 Tesla using modified blipped phase-encoding
✍ Scribed by Andreas Ebel; Norbert Schuff
- Publisher
- John Wiley and Sons
- Year
- 2007
- Tongue
- English
- Weight
- 412 KB
- Volume
- 58
- Category
- Article
- ISSN
- 0740-3194
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✦ Synopsis
Abstract
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.