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Yuval Zur 《Magnetic resonance in medicine》2011,66(6):1616-1626
Ghost artifacts are a serious issue in single and multi‐shot echo planar imaging. Because of these coherent artifacts, it is essential to consistently suppress the ghosts. In this article, we present a phase correction algorithm that achieves excellent ghost suppression for single and multi‐shot echo planar imaging. The phase correction is performed along both the x (read) direction and y (phase) direction. To this end, we apply a double field of view prescan and compute the phase required for ghost suppression. This phase is fitted to a 2D polynomial. The fitted phase is used to correct the echo planar imaging images. The correction algorithm can be used with any readout gradient polarities and any number of shots. A flow chart of the correction method is provided to better clarify the full process. Finally, phantom and volunteer images demonstrate the improvement of artifact suppression obtained with this algorithm over conventional phase correction methods. Magn Reson Med, 2011. © 2011 Wiley Periodicals, Inc. 相似文献
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Peripheral nerve stimulation characteristics of an asymmetric head‐only gradient coil compatible with a high‐channel‐count receiver array 下载免费PDF全文
Seung‐Kyun Lee Jean‐Baptiste Mathieu Dominic Graziani Joseph Piel Eric Budesheim Eric Fiveland Christopher J. Hardy Ek Tsoon Tan Bruce Amm Thomas K.‐F. Foo Matt A. Bernstein John Huston III Yunhong Shu John F. Schenck 《Magnetic resonance in medicine》2016,76(6):1939-1950
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Gregory J. Metzger Edward J. Auerbach Can Akgun Josh Simonson Xiaoming Bi Kâmil Uğurbil Pierre‐François van de Moortele 《Magnetic resonance in medicine》2013,69(1):114-126
The purpose of this study was to detail a strategy for performing non‐contrast enhanced renal magnetic resonance angiography studies at 7.0 T. It is demonstrated that with proper B management, these studies can be successfully performed at ultrahigh field within local specific absorption rate constraints. An inversion prepared gradient echo acquisition, standard for non‐contrast renal magnetic resonance angiography studies, required radiofrequency pulse specific B shimming solutions to be dynamically applied to address the field dependent increases in both B0 and B inhomogeneity as well as to accommodate limitation in available power. By using more efficient B shimming solutions for the inversion preparation and more homogeneous solutions for the excitation, high quality images of the renal arteries were obtained without venous and background signal artifacts while working within hardware and safety constraints. Finite difference time domain simulations confirmed in vivo measurements with respect to B distributions and homogeneity for the range of shimming strategies used and allowed the calculation of peak local specific absorption rate values normalized by input power and B. Increasing B homogeneity was accompanied by decreasing local specific absorption rate per Watt and increasing maximum local specific absorption rate per [B]2, which must be considered, along with body size and respiratory rate, when finalizing acquisition parameters for a given individual. Magn Reson Med, 2013. © 2012 Wiley Periodicals, Inc. 相似文献