Crivello Fabrice, Schormann Thorsten, Tzourio-Mazoyer Nathalie, Roland Per E, Zilles Karl, Mazoyer Bernard M
Groupe d'Imagerie Neurofonctionnelle, UMR 6095, CNRS-CEA LRC36V Université de Caen & Paris 5, Caen, France.
Hum Brain Mapp. 2002 Aug;16(4):228-50. doi: 10.1002/hbm.10047.
The alignment accuracy and impact on functional maps of four spatial normalization procedures have been compared using a set of high resolution brain MRIs and functional PET volumes acquired in 20 subjects. Simple affine (AFF), fifth order polynomial warp (WRP), discrete cosine basis functions (SPM), and a movement model based on full multi grid (FMG) approaches were applied on the same dataset for warping individual volumes onto the Human Brain Atlas (HBA) template. Intersubject averaged structural volumes and tissue probability maps were compared across normalization methods and to the standard brain. Thanks to the large number of degrees of freedom of the technique, FMG was found to provide enhanced alignment accuracy as compared to the other three methods, both for the grey and white matter tissues; WRP and SPM exhibited very similar performances whereas AFF had the lowest registration accuracy. SPM, however, was found to perform better than the other methods for the intra-cerebral cerebrospinal fluid (mainly in the ventricular compartments). Limited differences in terms of activation morphology and detection sensitivity were found between low resolution functional maps (FWHM approximately 10 mm) spatially normalized with the four methods, which overlapped in 42.8% of the total activation volume. These findings suggest that the functional variability is much larger than the anatomical one and that precise alignment of anatomical features has low influence on the resulting intersubject functional maps. When increasing the spatial resolution to approximately 6 mm, however, differences in localization of activated areas appear as a consequence of the different spatial normalization procedure used, restricting the overlap of the normalized activated volumes to only 6.2%.
使用20名受试者获取的一组高分辨率脑磁共振成像（MRI）和功能正电子发射断层扫描（PET）体积数据，比较了四种空间归一化程序的对齐精度及其对功能图谱的影响。简单仿射变换（AFF）、五阶多项式变形（WRP）、离散余弦基函数（SPM）以及基于全多网格（FMG）方法的运动模型，被应用于同一数据集，将个体体积数据扭曲到人类脑图谱（HBA）模板上。跨归一化方法并与标准脑比较了受试者间平均结构体积和组织概率图谱。由于该技术具有大量自由度，发现与其他三种方法相比，FMG在灰质和白质组织方面均提供了更高的对齐精度；WRP和SPM表现出非常相似的性能，而AFF的配准精度最低。然而，发现SPM在脑室内脑脊液（主要在脑室区域）方面比其他方法表现更好。在用这四种方法进行空间归一化的低分辨率功能图谱（半高宽约10毫米）之间，在激活形态和检测灵敏度方面发现有限差异，这些图谱在总激活体积的42.8%中重叠。这些发现表明，功能变异性远大于解剖变异性，并且解剖特征的精确对齐对所得受试者间功能图谱的影响较小。然而，当将空间分辨率提高到约6毫米时，由于使用了不同的空间归一化程序，激活区域的定位出现差异，使归一化激活体积的重叠率仅为6.2%。
