A study of rotationally invariant and symmetric indices of diffusion anisotropy
A study of rotationally invariant and symmetric indices of diffusion anisotropy
复制标题
DOI：
10.1016/s0730-725x(99)00029-6
复制
发表时间：
1999-07-01
影响因子：
2.5
通讯作者：
Carpenter, TA
中科院分区：
文献类型：
--
作者：
Papadakis, NG;Xing, D;Carpenter, TA
本研究探讨了一类旋转不变和对称（相对于主扩散系数）的水自扩散的各向异性指数，即分数各向异性（FA），相对各向异性（RA），和体积比（VR）的属性，特别强调其测量在脑组织中。一个简化的理论分析预测显着差异的各向异性指数（AI）的分布的主要扩散系数的敏感性。计算机模拟被用来研究三种磁共振（MR）扩散张量成像（DTI）采集方案对AI图像质量的影响，其中一种是新颖的：在形状和空间方向不同的大脑模型纤维上模拟这些方案。理论预测和模拟的结果证实了实验确定的空间地图的AI在体内正常猫的大脑。我们发现，FA映射的扩散各向异性与最大的细节和SNR，而VR提供了最强的对比度之间的低和高各向异性地区的代价增加噪声污染和降低分辨率的各向异性区域。RA证明质量中等。通过更密集和均匀地采样有效扩散椭球的空间，并需要相同的总成像时间的公布计划，新的DTI计划实现了更大的旋转不变性比公布的计划，改善噪声特性，从而提高图像质量的AI检查。我们的研究结果表明，扩散各向异性映射的显着改善是可能的，并为特定应用选择最合适的AI提供标准。(C)1999 Elsevier Science Inc.
This study investigated the properties of a class of rotationally invariant and symmetric (relative to the principal diffusivities) indices of the anisotropy of water self-diffusion, namely fractional anisotropy (FA), relative anisotropy (RA), and volume ratio (VR), with particular emphasis to their measurement in brain tissues. A simplified theoretical analysis predicted significant differences in the sensitivities of the anisotropy indices (AI) over the distribution of the principal diffusivities. Computer simulations were used to investigate the effects on AI image quality of three magnetic resonance (MR) diffusion tensor imaging (DTI) acquisition schemes, one being novel: the schemes were simulated on cerebral model fibres varying in shape and spatial orientation. The theoretical predictions and the results of the simulations were corroborated by experimentally determined spatial maps of the AI in a normal feline brain in vivo. We found that FA mapped diffusion anisotropy with the greatest detail and SNR whereas VR provided the strongest contrast between low- and high-anisotropy areas at the expense of increased noise contamination and decreased resolution in anisotropic regions. RA proved intermediate in quality. By sampling the space of the effective diffusion ellipsoid more densely and uniformly and requiring the same total imaging time as the published schemes, the novel DTI scheme achieved greater rotational invariance than the published schemes, with improved noise characteristics, resulting in improved image quality of the AI examined. Our findings suggest that significant improvements in diffusion anisotropy mapping are possible and provide criteria for the selection of the most appropriate AI for a particular application. (C) 1999 Elsevier Science Inc.