School of Electrical and Computer Engineering, Purdue University, West Lafayette, IN, 47907, USA.
Weldon School of Biomedical Engineering, Purdue University, 206 S. Martin Jischke Drive, West Lafayette, IN, 47907-2032, USA.
Sci Rep. 2021 Mar 26;11(1):7011. doi: 10.1038/s41598-021-86402-z.
A "carpet plot" is a 2-dimensional plot (time vs. voxel) of scaled fMRI voxel intensity values. Low frequency oscillations (LFOs) can be successfully identified from BOLD fMRI and used to study characteristics of neuronal and physiological activity. Here, we evaluate the use of carpet plots paired with a developed slope-detection algorithm as a means to study LFOs in resting state fMRI (rs-fMRI) data with the help of dynamic susceptibility contrast (DSC) MRI data. Carpet plots were constructed by ordering voxels according to signal delay time for each voxel. The slope-detection algorithm was used to identify and calculate propagation times, or "transit times", of tilted vertical edges across which a sudden signal change was observed. We aim to show that this metric has applications in understanding LFOs in fMRI data, possibly reflecting changes in blood flow speed during the scan, and for evaluating alternative blood-tracking contrast agents such as inhaled CO. We demonstrate that the propagations of LFOs can be visualized and automatically identified in a carpet plot as tilted lines of sudden intensity change. Resting state carpet plots produce edges with transit times similar to those of DSC carpet plots. Additionally, resting state carpet plots indicate that edge transit times vary at different time points during the scan.
“地毯图”是一种二维图（时间与体素），用于显示经比例缩放后的 fMRI 体素强度值。低频振荡（LFO）可从 BOLD fMRI 中成功识别，并用于研究神经元和生理活动的特征。在这里，我们借助动态磁敏感对比（DSC）MRI 数据，评估了使用地毯图与开发的斜率检测算法相结合的方法，以研究静息态 fMRI（rs-fMRI）数据中的 LFO。地毯图通过为每个体素的信号延迟时间对体素进行排序来构建。斜率检测算法用于识别和计算倾斜垂直边缘的传播时间或“传输时间”，观察到垂直边缘上突然发生信号变化。我们旨在表明，该指标可用于理解 fMRI 数据中的 LFO，可能反映了扫描过程中血流速度的变化，并可用于评估替代的血液追踪对比剂，如吸入的 CO。我们证明，LFO 的传播可以在地毯图中可视化并自动识别为突然强度变化的倾斜线。静息状态地毯图产生的边缘的传输时间与 DSC 地毯图的传输时间相似。此外，静息状态地毯图表明，边缘传输时间在扫描过程中的不同时间点会发生变化。
