Tong Yunjie, Lindsey Kimberly P, Hocke Lia M, Vitaliano Gordana, Mintzopoulos Dionyssios, Frederick Blaise deB
1 McLean Imaging Center, McLean Hospital, Belmont, MA, USA.
2 Department of Psychiatry, Harvard University Medical School, Boston, MA, USA.
J Cereb Blood Flow Metab. 2017 Feb;37(2):564-576. doi: 10.1177/0271678X16631755. Epub 2016 Jul 20.
It is widely known that blood oxygenation level dependent (BOLD) contrast in functional magnetic resonance imaging (fMRI) is an indirect measure for neuronal activations through neurovascular coupling. The BOLD signal is also influenced by many non-neuronal physiological fluctuations. In previous resting state (RS) fMRI studies, we have identified a moving systemic low frequency oscillation (sLFO) in BOLD signal and were able to track its passage through the brain. We hypothesized that this seemingly intrinsic signal moves with the blood, and therefore, its dynamic patterns represent cerebral blood flow. In this study, we tested this hypothesis by performing Dynamic Susceptibility Contrast (DSC) MRI scans (i.e. bolus tracking) following the RS scans on eight healthy subjects. The dynamic patterns of sLFO derived from RS data were compared with the bolus flow visually and quantitatively. We found that the flow of sLFO derived from RS fMRI does to a large extent represent the blood flow measured with DSC. The small differences, we hypothesize, are largely due to the difference between the methods in their sensitivity to different vessel types. We conclude that the flow of sLFO in RS visualized by our time delay method represents the blood flow in the capillaries and veins in the brain.
众所周知,功能磁共振成像(fMRI)中的血氧水平依赖(BOLD)对比度是通过神经血管耦合对神经元激活的一种间接测量。BOLD信号也受到许多非神经元生理波动的影响。在先前的静息态(RS)fMRI研究中,我们在BOLD信号中识别出一种移动的全身低频振荡(sLFO),并能够追踪其在大脑中的传播。我们假设这种看似内在的信号随血液移动,因此,其动态模式代表脑血流量。在本研究中,我们通过对八名健康受试者在RS扫描后进行动态磁敏感对比(DSC)MRI扫描(即团注追踪)来验证这一假设。将从RS数据中得出的sLFO的动态模式与团注流进行视觉和定量比较。我们发现,从RS fMRI得出的sLFO流在很大程度上代表了用DSC测量的血流量。我们推测,这些小差异很大程度上是由于两种方法对不同血管类型的敏感性不同所致。我们得出结论,通过我们的时间延迟方法可视化的RS中sLFO的流动代表了大脑中毛细血管和静脉中的血流量。