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fMRI BOLD contrast relationship to cerebrovascular tone

fMRI BOLD 对比与脑血管张力的关系

基本信息

批准号：
7098865
负责人：
TODD B PARRISH
金额：
$ 36.25万
依托单位：
NORTHWESTERN UNIVERSITY AT CHICAGO
依托单位国家：
美国
项目类别：
财政年份：
2003
资助国家：
美国
起止时间：
2003-09-27 至 2008-07-31
项目状态：
已结题

项目摘要

DESCRIPTION (provided by applicant): Functional magnetic resonance imaging (fMRI) relies on the coupling of blood flow changes to neuronal activity. These blood flow changes in turn alter the concentration of oxygen in the local blood pool surrounding the neurons. Because the susceptibility of oxyhemoglobin and deoxyhemoglobin are different, it is possible to make the MR signal sensitive to oxygen concentration; this is termed blood oxygenation level dependent (BOLD) signal. The BOLD signal change from the rest condition to the active condition is approximately 1-3%. Detection of the BOLD signal requires a robust paradigm, preprocessing of the signal, and statistical modeling to generate activation maps. All of this is necessary because of the weak BOLD contrast that exists in hemodynamically normal subjects. When a subject has compromised vasculature and impaired vasoreactivity from a carotid stenosis or occlusion, we have demonstrated that the BOLD signal response is absent or severely altered beyond normal detection. This is a very important issue as fMRI moves into the clinical setting and is used to study stroke recovery or aging populations. For example, in stroke recovery one may detect activation increases over time and assume they are due to neuronal recruitment or rehabilitation; however, the activations may be the result of developing collateral flow or recovery of vasoreactivity. One of the goals of this proposal is to investigate and characterize the BOLD response in the face of altered hemodynamics. A limitation to the field of functional MRI is the small difference in BOLD signal used to detect activations. We have shown that the physiologic interaction of caffeine signigicantly increases the BOLD contrast (-40% at 1,5T and 80-170% at 3T). In this proposal, the mechanisms of caffeine will be explored in normal subjects using fMRI, MR based perfusion and transcranial Doppler ultrasound to characterize the BOLD signal and the cerebral blood flow response. Individual components will be invesitgated in order to create a simple model of the interations with BOLD contrast. The improvement in BOLD contrast can be used to improve the temporal and spatial resolution or to allow the investigation of more subtle cognitive paradigms.The theme of this proposal is to investigate the impact of physiologic mechanisms (reactivity, flow, hematocrit, neuronal activity) on the generation of BOLD signal and more importantly BOLD contrast.

描述（由申请人提供）：功能性磁共振成像（fMRI）依赖于血流变化与神经元活动的耦合。这些血流的变化反过来又改变了神经元周围局部血池中的氧浓度。由于氧合血红蛋白和脱氧血红蛋白的敏感性不同，有可能使MR信号对氧浓度敏感；这被称为血氧水平依赖（BOLD）信号。BOLD信号从静止状态到活动状态的变化约为1-3%。BOLD信号的检测需要一个健壮的范例、信号预处理和统计建模来生成激活图。所有这些都是必要的，因为血液动力学正常的受试者存在较弱的BOLD对比。当受试者因颈动脉狭窄或闭塞而血管系统受损和血管反应性受损时，我们已经证明BOLD信号反应缺失或严重改变，超出正常检测范围。这是一个非常重要的问题，因为功能磁共振成像进入临床环境，并用于研究中风恢复或人口老龄化。例如，在中风恢复过程中，人们可以检测到随着时间的推移激活增加，并假设它们是由于神经元的募集或康复；然而，激活可能是侧支血流发展或血管反应性恢复的结果。该建议的目标之一是研究和表征血液动力学改变时BOLD的反应。功能性MRI领域的一个限制是用于检测激活的BOLD信号的微小差异。我们已经证明，咖啡因的生理相互作用显著增加了BOLD对比（在1.5 t时-40%，在3T时80-170%）。在本研究中，我们将利用功能磁共振成像（fMRI）、基于MR的灌注和经颅多普勒超声（transcranial Doppler ultrasound）来表征BOLD信号和脑血流反应，探讨咖啡因在正常受试者中的作用机制。为了创建一个具有BOLD对比的简单的国际模型，我们将研究各个组件。BOLD对比的改善可以用来提高时间和空间分辨率，或者允许更微妙的认知范式的研究。本提案的主题是研究生理机制（反应性、血流、红细胞压积、神经元活动）对BOLD信号产生的影响，更重要的是BOLD对比。