Whole‐brain single‐shot STEAM DTI at 4 Tesla utilizing transverse coherences for enhanced SNR
Whole‐brain single‐shot STEAM DTI at 4 Tesla utilizing transverse coherences for enhanced SNR
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4 Tesla 的全脑单次 STEAM DTI 利用横向相干性增强 SNR
DOI：
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发表时间：
2009
影响因子：
3.3
通讯作者：
N. Shah
中科院分区：
文献类型：
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作者：
T. Stöcker;J. Kaffanke;N. Shah
扩散张量成像是无创获取人脑结构信息的重要方法。对于先进的光纤跟踪，必须沿着许多不同的空间方向采集扩散加权（DW）图像，从而导致扫描时间较长。因此，主要使用超快速成像方法，即平面回波成像（EPI），但该技术存在磁化率引起的图像伪影和几何失真的问题。这些问题在非常高的磁场强度下变得更加明显。在这方面，DW（单次 STEAM）是基于 EPI 的方法的一种有趣且快速的成像替代方法。 DW 单次 STEAM 能够采集无伪影的图像，尽管会降低信噪比 (SNR)，但可以通过利用高磁场来补偿。这里演示了 DW 单次 STEAM 在 4 特斯拉的应用。为了优化信噪比和分辨率特性，引入了一种新的可变翻转角计算算法，通过精确计算横向相干性来实现精确的信号演化计算。通过整合稳定的重聚焦横向磁化强度，省略射频 (RF) 破坏会导致 DW 信号大约增加两倍。该方法的优点在模拟和体内实验中得到了体现。磁共振医学 61:372–380, 2009。© 2009 Wiley‐Liss, Inc.
Diffusion tensor imaging is an important method for noninvasively acquiring structural information of the human brain. For advanced fiber tracking, the acquisition of diffusion‐weighted (DW) images has to be performed along many different spatial directions, resulting in long scan times. Therefore, the ultra‐fast imaging method, echo‐planar imaging (EPI), is mostly used, but this technique suffers from susceptibility‐induced image artefacts and geometric distortions. These problems become even more pronounced at very high magnetic field strengths. In this regard, DW, single‐shot STEAM is an interesting and rapid imaging alternative to EPI‐based methods. DW single‐shot STEAM enables the acquisition of artefact‐free images albeit at the expense of a reduced signal‐to‐noise ratio (SNR), which can be compensated by utilizing high magnetic fields. Here, the application of DW single‐shot STEAM at 4 Tesla is demonstrated. To optimize the SNR and the resolution properties, a new variable flip‐angle computational algorithm is introduced enabling accurate signal evolution computation with a precise calculation of transverse coherences. Omission of radiofrequency (RF) spoiling results in an approximate twofold increase of the DW signal by integration of the stable refocused transverse magnetization. The advantage of the approach is shown in simulations and in vivo experiments. Magn Reson Med 61:372–380, 2009. © 2009 Wiley‐Liss, Inc.