Boxerman J L, Bandettini P A, Kwong K K, Baker J R, Davis T L, Rosen B R, Weisskoff R M
NMR Center, Massachusetts General Hospital, Charlestown 02129, USA.
Magn Reson Med. 1995 Jul;34(1):4-10. doi: 10.1002/mrm.1910340103.
Understanding the relationship between fMRI signal changes and activated cortex is paramount to successful mapping of neuronal activity. To this end, the relative extravascular and intravascular contribution to fMRI signal change from capillaries (localized), venules (less localized) and macrovessels (remote, draining veins) must be determined. In this work, the authors assessed both the extravascular and intravascular contribution to blood oxygenation level-dependent gradient echo signal change at 1.5 T by using a Monte Carlo model for susceptibility-based contrast in conjunction with a physiological model for neuronal activation-induced changes in oxygenation and vascular volume fraction. The authors compared our Model results with experimental fMRI signal changes with and without velocity sensitization via bipolar gradients to null the intravascular signal. The model and experimental results are in agreement and suggest that the intravascular spins account for the majority of fMRI signal change on T2*-weighted images at 1.5 T.
了解功能磁共振成像（fMRI）信号变化与激活皮层之间的关系对于成功绘制神经元活动至关重要。为此，必须确定毛细血管（局部）、小静脉（局部性较差）和大血管（远端引流静脉）对fMRI信号变化的相对血管外和血管内贡献。在这项工作中，作者通过使用基于磁化率对比度的蒙特卡罗模型以及神经元激活诱导的氧合和血管体积分数变化的生理模型，评估了1.5T时血管外和血管内对血氧水平依赖梯度回波信号变化的贡献。作者将我们的模型结果与通过双极梯度进行速度敏感化（以消除血管内信号）和未进行速度敏感化时的实验性fMRI信号变化进行了比较。模型和实验结果一致，表明在1.5T的T2*加权图像上，血管内自旋占fMRI信号变化的大部分。
