Effects of diffusion weighting schemes on the reproducibility of DTI-derived fractional anisotropy, mean diffusivity, and principal eigenvector measurements at 1.5T
Effects of diffusion weighting schemes on the reproducibility of DTI-derived fractional anisotropy, mean diffusivity, and principal eigenvector measurements at 1.5T
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DOI：
10.1016/j.neuroimage.2007.02.056
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发表时间：
2007-07-15
期刊：
影响因子：
5.7
通讯作者：
Mori, Susumu
中科院分区：
文献类型：
--
作者：
Landman, Bennett A.;Farrell, Jonathan A. D.;Mori, Susumu
扩散张量成像（DTI）用于研究体内组织的组成和结构。为了提高DTI对比的信噪比（SNR），研究通常使用超过6个扩散加权（DW）方向的最小值，或获取同一组DW方向的重复观察结果。基于模拟的研究已经试图优化DTI采集，并建议增加DTI数据集的方向分辨率（即，不同方向的数目）优于在相等扫描时间比较中重复观察。然而，在考虑生理噪声和扫描仪稳定性时，如何将这些建议转化为实践并不总是很清楚。此外，不同DW方案对ht活体DTI结果的影响尚未完全了解。这项研究的特点是如何组成的DW计划，在方向的数量，影响在体内分数各向异性（FA），平均扩散率（MD），和主特征向量（PEV）的结果的精度和准确性。DTI可靠性的方向依赖性在体内证明，并提供了一个原则性的理论框架，以支持和解释与模拟结果的结果。只要采样方向平衡良好，由于不同的DW方案的DTI对比度的差异被证明是小的会话内变异。这些差异在低SNR下加重，而在高SNR下最小化。这一结果表明，典型的临床研究，使用类似的协议，但不同的细胞平衡的DW计划，很容易在实验精度相当。(C)2007爱思唯尔公司All rights reserved.
Diffusion tensor imaging (DTI) is used to study tissue composition and architecture in vivo. To increase the signal to noise ratio (SNR) of DTI contrasts, studies typically use more than the minimum of 6 diffusion weighting (DW) directions or acquire repeated observations of the same set of DW directions. Simulation-based studies have sought to optimize DTI acquisitions and suggest that increasing the directional resolution of a DTI dataset (i.e., the number of distinct directions) is preferable to repeating observations, in an equal scan time comparison. However, it is not always clear how to translate these recommendations into practice when considering physiological noise and scanner stability. Furthermore, the effect of different DW schemes on ht vivo DTI findings is not fully understood. This study characterizes how the makeup of a DW scheme, in terms of the number of directions, impacts the precision and accuracy of in vivo fractional anisotropy (FA), mean diffusivity, (MD), and principal eigenvector (PEV) findings. Orientation dependence of DTI reliability is demonstrated in vivo and a principled theoretical framework is provided to support and interpret findings with simulation results. As long as sampling orientations are well balanced, differences in DTI contrasts due to different DW schemes are shown to be small relative to intra-session variability. These differences are accentuated at low SNR, while minimized at high SNR. This result suggests that typical clinical studies, which use similar protocols but different ell-balanced DW schemes, are readily comparable within the experimental precision. (C) 2007 Elsevier Inc. All rights reserved.