A Simple Low-SAR Technique for Chemical-Shift Selection with High-Field Spin-Echo Imaging
A Simple Low-SAR Technique for Chemical-Shift Selection with High-Field Spin-Echo Imaging
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DOI：
10.1002/mrm.22518
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发表时间：
2010-08-01
影响因子：
3.3
通讯作者：
Turner, Robert
中科院分区：
文献类型：
--
作者：
Ivanov, Dimo;Schaefer, Andreas;Turner, Robert
我们发现了一种简单且高度稳健的方法，用于去除自旋回波 MR 图像中的化学位移伪影，同时降低射频功率沉积（比吸收率）。该方法在 7 T 采集的自旋回波回波平面成像大脑图像中得到了证明，完全抑制了头皮脂肪信号。当激发和重新聚焦脉冲的持续时间足够不同，因此其切片选择梯度的幅度也不同时，激发和重新聚焦的脂肪切片之间会产生空间失配，而没有重叠。由于没有使用额外的射频脉冲来抑制脂肪，因此与传统方法相比，特定吸收率显着降低。这使得单位时间内的体积覆盖范围更大，非常适合使用自旋回波平面成像进行功能和扩散研究。此外，该方法通常可以应用于涉及高磁场强度下的切片选择性激励和至少一个切片选择性重聚焦脉冲的任何序列。该方法比梯度反转方法更有效，并且对于静态（偏振）场 (B(0)) 的不均匀性更稳健。 Magn Reson Med 64:319-326, 2010。(C) 2010 Wiley-Liss, Inc.
We have discovered a simple and highly robust method for removal of chemical shift artifact in spin-echo MR images, which simultaneously decreases the radiofrequency power deposition (specific absorption rate). The method is demonstrated in spin-echo echo-planar imaging brain images acquired at 7 T, with complete suppression of scalp fat signal. When excitation and refocusing pulses are sufficiently different in duration, and thus also different in the amplitude of their slice-select gradients, a spatial mismatch is produced between the fat slices excited and refocused, with no overlap. Because no additional radiofrequency pulse is used to suppress fat, the specific absorption rate is significantly reduced compared with conventional approaches. This enables greater volume coverage per unit time, well suited for functional and diffusion studies using spin-echo echo-planar imaging. Moreover, the method can be generally applied to any sequence involving slice-selective excitation and at least one slice-selective refocusing pulse at high magnetic field strengths. The method is more efficient than gradient reversal methods and more robust against inhomogeneities of the static (polarizing) field (B(0)). Magn Reson Med 64:319-326, 2010. (C) 2010 Wiley-Liss, Inc.