Baudewig J, Dechent P, Merboldt K D, Frahm J
Biomedizinische NMR Forschungs GmbH am Max-Planck-Institut für biophysikalische Chemie, 37070 Göttingen, Germany.
Magn Reson Imaging. 2003 Dec;21(10):1121-30. doi: 10.1016/j.mri.2003.08.013.
The definition of objective and effective thresholds in MRI of human brain function is a crucial step in the analysis of paradigm-related activations. This paper introduces a user-independent and robust procedure that calculates statistical parametric maps based on correlation coefficients. Thresholds are introduced as p values and defined with respect to the physiologic noise distribution of the individual maps. Experimental examples from the human visual and motor system rely on dynamic acquisitions of gradient-echo echo-planar images (2.0 T, TR = 2,000 ms, 96 x 128 matrix) with blood oxygenation level-dependent contrast. The results demonstrate the disadvantages of thresholding with fixed correlation coefficients. In contrast, taking the individual noise into account allows for a derivation of p values and a reliable identification of highly significant activation centers. An adequate delineation of the spatial extent of activation may be achieved by adding directly neighboring pixels provided their correlation coefficients comply with a second lower p value threshold.
确定人脑功能磁共振成像（MRI）中客观有效的阈值是分析范式相关激活的关键步骤。本文介绍了一种独立于用户且稳健的程序，该程序基于相关系数计算统计参数图。阈值以p值的形式引入，并根据各个图的生理噪声分布来定义。来自人类视觉和运动系统的实验示例依赖于动态采集的梯度回波平面回波图像（2.0 T，TR = 2000 ms，96×128矩阵），具有血氧水平依赖对比。结果表明了使用固定相关系数进行阈值处理的缺点。相比之下，考虑个体噪声可以得出p值，并可靠地识别高度显著的激活中心。如果直接相邻像素的相关系数符合第二个较低的p值阈值，则通过添加这些像素可以实现对激活空间范围的适当描绘。
