Diffusion anisotropy measurement of brain white matter is affected by voxel size: Underestimation occurs in areas with crossing fibers
Diffusion anisotropy measurement of brain white matter is affected by voxel size: Underestimation occurs in areas with crossing fibers
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DOI：
10.3174/ajnr.a0488
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发表时间：
2007-06-01
影响因子：
3.5
通讯作者：
Nishimura, T.
中科院分区：
文献类型：
--
作者：
Oouchi, H.;Yamada, K.;Nishimura, T.
背景和目的：扩散张量成像（DTI）的体素大小/形状可能直接影响交叉纤维区域的各向异性分数（FA）的测量，本文的目的是研究体素大小/形状对使用各向同性和非各向同性体素测量FA的影响。材料和方法：10名健康成人志愿者使用1.5T临床成像仪进行MR成像。使用2种不同的体素尺寸进行DTI：2 mm截面的各向同性体素（2 X 2 X 2 mm（3））和6 mm截面的非各向同性体素（2 X 2 X 6 mm（3））。使用单次激发回波平面成像技术获得图像，在15个方向上使用运动探测梯度，b值为1000 S/mm（2）。结果：各向同性体素越小，在上级纵束、丘脑、红核等交叉纤维区FA值越大;在没有交叉纤维的区域，如胼胝体，内囊后肢，皮质脊髓束位于半卵圆中心水平（P > 0.05）。ADC值不受体素的大小/形状在任何测量大脑的区域，measured.CONCLUSION：FA值，测量在包含交叉纤维的区域被低估时，使用各向异性DTI。
BACKGROUND AND PURPOSE: Voxel size/shape of diffusion tensor imaging (DTI) may directly affect the measurement of fractional anisotropy (FA) in regions where there are crossing fibers, The purpose of this article was to investigate the effect of voxel size/shape on measured FA by using isotropic and nonisotropic voxels.MATERIALS AND METHODS: Ten healthy adult volunteers had MR imaging by using a 1.5T clinical imager. DTI was performed with 2 different voxel sizes: a 2-mm-section isotropic voxel (2 X 2 X 2 mm(3)) and a 6-mm-section nonisotropic voxel (2 X 2 X 6 mm(3)). Images were obtained by using a single-shot echoplanar imaging technique with motion-probing gradients in 15 orientations and a b-value of 1000 S/mm(2). FA and the apparent diffusion coefficient (ADC) were measured at different sites of the brain.RESULTS: When smaller isotropic voxels were used, the FA was greater in areas with crossing fibers, including the superior longitudinal fasciculus, the thalamus, and the red nucleus; the FA was not significantly different in areas without crossing fibers, such as the corpus callosum, the posterior limb of the internal capsule, and the corticospinal tract at the level of the centrum semiovale (P >.05). The ADC values were not affected by voxel size/shape at any of the areas of the brain that were measured.CONCLUSION: FA values that are measured in regions containing crossing fibers are underestimated when using nonisotropic DTI.