Functional magnetic resonance Imaging based on changes in vascular space occupancy
Functional magnetic resonance Imaging based on changes in vascular space occupancy
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DOI：
10.1002/mrm.10519
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发表时间：
2003-08-01
影响因子：
3.3
通讯作者：
van Zijl, PCM
中科院分区：
文献类型：
--
作者：
Lu, H;Golay, X;van Zijl, PCM
在大脑激活期间，通过微血管扩张和收缩促进氧气输送的局部控制。一种新的功能磁共振成像（fMRI）的方法是敏感的，这些微血管的调整。这种对比是通过以独立于血液氧合和血流的方式消除血液信号来实现的。因此，脑血容量（CBV）的变化可以通过剩余的血管外水信号（即，实质组织），而不需要外源性造影剂或任何其它侵入性过程。这种血管空间占用（VASO）依赖性功能性MRI（fMRI）方法的可行性证明了视觉刺激，屏气（高碳酸血症）和过度通气（低碳酸血症）。在视觉刺激和屏气期间，VASO信号显示出与刺激范例的负相关性，与局部血管舒张一致。这种效应在过度换气时逆转。VASO-fMRI、基于脑血流（CBF）的fMRI和血氧水平依赖（BOLD）fMRI的血流动力学反应的比较表明VASO的小动脉和小静脉的时间特征。经计算，水交换速率变化和CSF部分体积污染的影响可忽略不计。在常用的fMRI分辨率为3.75 x 3.75 x 5 mm（3）时，VASO-fMRI的对比度噪声比（CNR）与基于CBF的fMRI相当，但比BOLD-fMRI低3倍。支持一个更好的灰质定位的VASO-fMRI方法相比，BOLD的参数。(C)2003 Wiley-Liss，Inc.
During brain activation, local control of oxygen delivery is facilitated through microvascular dilatation and constriction. A new functional MRI (fMRI) methodology is reported that is sensitive to these microvascular adjustments. This contrast is accomplished by eliminating the blood signal in a manner that is independent of blood oxygenation and flow. As a consequence, changes in cerebral blood volume (CBV) can be assessed through changes in the remaining extravascular water signal (i.e., that of parenchymal tissue) without need for exogenous contrast agents or any other invasive procedures. The feasibility of this vascular space occupancy (VASO) -dependent functional MRI (fMRI) approach is demonstrated for visual stimulation, breath-hold (hypercapnia), and hyperventilation (hypocapnia). During visual stimulation and breath-hold, the VASO signal shows an inverse correlation with the stimulus paradigm, consistent with local vasodilatation. This effect is reversed during hyperventilation. Comparison of the hemodynamic responses of VASO-fMRI, cerebral blood flow (CBF)-based fMRI, and blood oxygenation level-dependent (BOLD) fMRI indicates both arteriolar and venular temporal characteristics in VASO. The effect of changes in water exchange rate and partial volume contamination with CSF were calculated to be negligible. At the commonly-used fMRI resolution of 3.75 x 3.75 x 5 mm(3), the contrast-to-noise-ratio (CNR) of VASO-fMRI was comparable to that of CBF-based fMRI, but a factor of 3 lower than for BOLD-fMRI. Arguments supporting a better gray matter localization for the VASO-fMRI approach compared to BOLD are provided. (C) 2003 Wiley-Liss, Inc.