FUNCTIONAL BRAIN MAPPING BY BLOOD OXYGENATION LEVEL-DEPENDENT CONTRAST MAGNETIC-RESONANCE-IMAGING - A COMPARISON OF SIGNAL CHARACTERISTICS WITH A BIOPHYSICAL MODEL
FUNCTIONAL BRAIN MAPPING BY BLOOD OXYGENATION LEVEL-DEPENDENT CONTRAST MAGNETIC-RESONANCE-IMAGING - A COMPARISON OF SIGNAL CHARACTERISTICS WITH A BIOPHYSICAL MODEL
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DOI：
10.1016/s0006-3495(93)81441-3
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发表时间：
1993-03-01
影响因子：
3.4
通讯作者：
UGURBIL, K
中科院分区：
文献类型：
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作者：
OGAWA, S;MENON, RS;UGURBIL, K
最近已经证明，磁共振成像可以用来绘制人类心理操作产生的大脑血流动力学的变化。正在开发的一种方法依赖于血氧水平依赖性（BOLD）对比度：静脉血脱氧血红蛋白的顺磁效应产生的脑水质子信号强度的变化。在这里，我们讨论观察到的基于 BOLD 的信号变化的基本定量特征，包括信号幅度及其磁场依赖性和动态效应，例如在光刺激实验期间在初级视觉皮层的信号中诱发的明显振荡模式。将观察到的特征与附近静脉血管中顺磁性脱氧血红蛋白产生的局部场梯度产生的水质子体素内相分散的蒙特卡罗模拟结果进行比较。模拟表明，对于毛细血管来说，水分子扩散的影响很强，但是对于较大的静脉血管，水扩散并不是脱氧血红蛋白引起的信号相移的重要决定因素。我们根据主磁场强度、静脉血的氧合程度、组织中的静脉血体积分数和血管的尺寸提供了表观面内弛豫率常数 (R2*) 的表达式。
It recently has been demonstrated that magnetic resonance imaging can be used to map changes in brain hemodynamics produced by human mental operations. One method under development relies on blood oxygenation level-dependent (BOLD) contrast: a change in the signal strength of brain water protons produced by the paramagnetic effects of venous blood deoxyhemoglobin. Here we discuss the basic quantitative features of the observed BOLD-based signal changes, including the signal amplitude and its magnetic field dependence and dynamic effects such as a pronounced oscillatory pattern that is induced in the signal from primary visual cortex during photic stimulation experiments. The observed features are compared with the results of Monte Carlo simulations of water proton intravoxel phase dispersion produced by local field gradients generated by paramagnetic deoxyhemoglobin in nearby venous blood vessels. The simulations suggest that the effect of water molecule diffusion is strong for the case of blood capillaries, but, for larger venous blood vessels, water diffusion is not an important determinant of deoxyhemoglobin-induced signal dephasing. We provide an expression for the apparent in-plane relaxation rate constant (R2*) in terms of the main magnetic field strength, the degree of the oxygenation of the venous blood, the venous blood volume fraction in the tissue, and the size of the blood vessel.