MARBILab, Museo storico della fisica e Centro di studi e ricerche Enrico Fermi, c/o Fondazione Santa Lucia, Roma, Italy.
J Magn Reson Imaging. 2010 Mar;31(3):690-7. doi: 10.1002/jmri.22040.
To compare the effects of anisotropic and Gaussian smoothing on the outcomes of diffusion tensor imaging (DTI) voxel-based (VB) analyses in the clinic, in terms of signal-to-noise ratio (SNR) enhancement and directional information and boundary structures preservation.
DTI data of 30 Alzheimer's disease (AD) patients and 30 matched control subjects were obtained at 3T. Fractional anisotropy (FA) maps with variable degrees and quality (Gaussian and anisotropic) of smoothing were created and compared with an unsmoothed dataset. The two smoothing approaches were evaluated in terms of SNR improvements, capability to separate differential effects between patients and controls by a standard VB analysis, and level of artifacts introduced by the preprocessing.
Gaussian smoothing regionally biased the FA values and introduced a high variability of results in clinical analysis, greatly dependent on the kernel size. On the contrary, anisotropic smoothing proved itself capable of enhancing the SNR of images and maintaining boundary structures, with only moderate dependence of results on smoothing parameters.
Our study suggests that anisotropic smoothing is more suitable in DTI studies; however, regardless of technique, a moderate level of smoothing seems to be preferable considering the artifacts introduced by this manipulation.
比较各向异性平滑和高斯平滑对基于体素（voxel-based，VB）的弥散张量成像（diffusion tensor imaging，DTI）分析结果的影响，从信噪比（signal-to-noise ratio，SNR）增强、方向信息和边界结构保留等方面进行评估。
在 3T 扫描仪上采集 30 例阿尔茨海默病（Alzheimer's disease，AD）患者和 30 例匹配对照者的 DTI 数据。生成具有不同程度和质量（高斯和各向异性）平滑的各向异性分数（fractional anisotropy，FA）图，并与未平滑数据集进行比较。从 SNR 改善、标准 VB 分析区分患者和对照组之间差异的能力，以及预处理引入的伪影水平等方面，对两种平滑方法进行评估。
高斯平滑使 FA 值产生局部偏差，并在临床分析中引入了高变异性的结果，这极大地依赖于核大小。相反，各向异性平滑能够增强图像的 SNR 并保持边界结构，其结果仅对平滑参数有适度的依赖性。
本研究表明，在 DTI 研究中，各向异性平滑更为适用；然而，无论采用何种技术，考虑到这种操作引入的伪影，适度的平滑水平似乎更为可取。
