DeDora Daniel J, Nedic Sanja, Katti Pratha, Arnab Shafique, Wald Lawrence L, Takahashi Atsushi, Van Dijk Koene R A, Strey Helmut H, Mujica-Parodi Lilianne R
Department of Biomedical Engineering, Stony Brook University School of Medicine Stony Brook, NY, USA.
Department of Radiology, Athinoula A. Martinos Center for Biomedical Imaging, Massachusetts General HospitalCharlestown, MA, USA; Department of Radiology, Harvard Medical SchoolBoston, MA, USA; Harvard-MIT Division of Health Sciences and Technology, Massachusetts Institute of TechnologyCambridge, MA, USA.
Front Neurosci. 2016 May 4;10:180. doi: 10.3389/fnins.2016.00180. eCollection 2016.
Task-free connectivity analyses have emerged as a powerful tool in functional neuroimaging. Because the cross-correlations that underlie connectivity measures are sensitive to distortion of time-series, here we used a novel dynamic phantom to provide a ground truth for dynamic fidelity between blood oxygen level dependent (BOLD)-like inputs and fMRI outputs. We found that the de facto quality-metric for task-free fMRI, temporal signal to noise ratio (tSNR), correlated inversely with dynamic fidelity; thus, studies optimized for tSNR actually produced time-series that showed the greatest distortion of signal dynamics. Instead, the phantom showed that dynamic fidelity is reasonably approximated by a measure that, unlike tSNR, dissociates signal dynamics from scanner artifact. We then tested this measure, signal fluctuation sensitivity (SFS), against human resting-state data. As predicted by the phantom, SFS-and not tSNR-is associated with enhanced sensitivity to both local and long-range connectivity within the brain's default mode network.
无任务连接性分析已成为功能神经成像中的一种强大工具。由于构成连接性测量基础的互相关性对时间序列的失真很敏感，因此我们在这里使用了一种新型动态体模，为血氧水平依赖（BOLD）样输入与功能磁共振成像（fMRI）输出之间的动态保真度提供一个基本事实。我们发现，无任务fMRI的实际质量指标——时间信噪比（tSNR）与动态保真度呈负相关；因此，针对tSNR进行优化的研究实际上产生的时间序列显示出信号动态的最大失真。相反，该体模表明，一种测量方法可以合理地近似动态保真度，与tSNR不同，这种测量方法将信号动态与扫描仪伪影区分开来。然后，我们针对人类静息态数据测试了这种测量方法——信号波动敏感性（SFS）。正如体模所预测的那样，与大脑默认模式网络内的局部和远程连接增强敏感性相关的是SFS，而不是tSNR。
