Impact of acquisition and analysis strategies on cortical depth-dependent fMRI
Impact of acquisition and analysis strategies on cortical depth-dependent fMRI
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DOI：
10.1016/j.neuroimage.2017.05.022
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发表时间：
2018-03-01
期刊：
影响因子：
5.7
通讯作者：
Uludag, Kamil
中科院分区：
文献类型：
--
作者：
Kashyap, Sriranga;Ivanov, Dimo;Uludag, Kamil
在超高磁场（>= 7 T）下的功能性MRI提供了在亚毫米空间尺度下探测人脑中活体柱状和层状加工的机会。然而，由于梯度和自旋回波BOLD fMRI固有的上行静脉和软脑膜静脉的偏倚，fMRI数据只能间接反映神经元层的轮廓。此外，由于相对较大的体素尺寸和功能图像中缺乏足够的组织对比度，难以准确描绘皮质深度。在传统的深度依赖性功能磁共振成像研究中，解剖和功能数据是用不同的图像读出模块采集的，功能磁共振成像数据是失真校正的，血管偏差是通过减去不同刺激条件下的深度依赖性激活曲线来解释的。在这项研究中，使用高分辨率梯度回波功能磁共振成像数据（0.7毫米各向同性）的人类视觉皮层，我们建议，而不是，深度依赖的功能信息是最好的保存，如果数据分析是在原始的功能数据空间。为了实现这一点，我们获得了解剖图像与高组织对比度和类似的失真的功能图像使用多个反转恢复时间EPI，从而消除了需要去扭曲的fMRI数据。我们证明了更高的空间精度的皮质层定义的这种方法相比，更传统的方法，使用MP2神经解剖。此外，我们提供的理论论据和经验证据表明，血管偏差可以更好地占使用除法，而不是减法的深度依赖的配置文件。最后，我们表明，脑灰质的血流动力学反应具有相对较强的刺激后下冲比软脑膜静脉体素。总之，我们表明，功能磁共振成像数据采集和处理的选择可以影响可观察到的差异，在皮层的深度配置文件和目前的证据表明，皮质深度依赖调制的BOLD信号可以解决使用梯度回波成像。
Functional MRI at ultra-high magnetic fields (>= 7 T) provides the opportunity to probe columnar and laminar processing in the human brain in vivo at sub-millimeter spatial scales. However, fMRI data only indirectly reflects the neuronal laminar profile due to a bias to ascending and pial veins inherent in gradient-and spinecho BOLD fMRI. In addition, accurate delineation of the cortical depths is difficult, due to the relatively large voxel sizes and lack of sufficient tissue contrast in the functional images. In conventional depth-dependent fMRI studies, anatomical and functional data are acquired with different image read-out modules, the fMRI data are distortion-corrected and vascular biases are accounted for by subtracting the depth-dependent activation profiles of different stimulus conditions. In this study, using high-resolution gradient-echo fMRI data (0.7 mm isotropic) of the human visual cortex, we propose instead, that depth-dependent functional information is best preserved if data analysis is performed in the original functional data space. To achieve this, we acquired anatomical images with high tissue contrast and similar distortion to the functional images using multiple inversion-recovery time EPI, thereby eliminating the need to un-distort the fMRI data. We demonstrate higher spatial accuracy for the cortical layer definitions of this approach as compared to the more conventional approach using MP2RAGE anatomy. In addition, we provide theoretical arguments and empirical evidence that vascular biases can be better accounted for using division instead of subtraction of the depth-dependent profiles. Finally, we show that the hemodynamic response of grey matter has relatively stronger post-stimulus undershoot than the pial vein voxels. In summary, we show that the choice of fMRI data acquisition and processing can impact observable differences in the cortical depth profiles and present evidence that cortical depth-dependent modulation of the BOLD signal can be resolved using gradient-echo imaging.