Rostrup E, Law I, Blinkenberg M, Larsson H B, Born A P, Holm S, Paulson O B
Danish Research Center of Magnetic Resonance, Hvidovre Hospital, Hvidovre, DK-2650, Denmark.
Neuroimage. 2000 Feb;11(2):87-97. doi: 10.1006/nimg.1999.0526.
Previous fMRI studies of the cerebrovascular response to hypercapnia have shown signal change in cerebral gray matter, but not in white matter. Therefore, the objective of the present study was to compare (15)O PET and T *(2)-weighted MRI during a hypercapnic challenge. The measurements were performed under similar conditions of hypercapnia, which were induced by inhalation of 5 or 7% CO(2). The baseline rCBF values were 65.1 ml hg(-1) min(-1) for temporal gray matter and 28.7 ml hg(-1) min(-1) for white matter. By linear regression, the increases in rCBF during hypercapnia were 23.0 and 7. 2 ml hg(-1) min(-1) kPa(-1) for gray and white matter. The signal changes were 6.9 and 1.9% for the FLASH sequence and were 3.8 and 1. 7% for the EPI sequence at comparable echo times. The regional differences in percentage signal change were significantly reduced when normalized by regional flow values. A deconvolution analysis is introduced to model the relation between fMRI signal and end-expiratory CO(2) level. Temporal parameters, such as mean transit time, were derived from this analysis and suggested a slower response in white matter than in gray matter regions. It was concluded that the differences in the magnitude of the fMRI response can largely be attributed to differences in flow and that there is a considerable difference in the time course of the response between gray and white matter.
先前关于高碳酸血症脑血管反应的功能磁共振成像（fMRI）研究显示，脑灰质有信号变化，而白质没有。因此，本研究的目的是比较高碳酸血症激发试验期间的（15）O正电子发射断层扫描（PET）和T*（2）加权磁共振成像（MRI）。测量在相似的高碳酸血症条件下进行，通过吸入5%或7%的二氧化碳来诱发。颞叶灰质的基线脑血流量（rCBF）值为65.1 ml hg（-1）min（-1），白质为28.7 ml hg（-1）min（-1）。通过线性回归，高碳酸血症期间灰质和白质的rCBF增加分别为23.0和7.2 ml hg（-1）min（-1）kPa（-1）。在相当的回波时间下，快速成像（FLASH）序列的信号变化分别为6.9%和1.9%，回波平面成像（EPI）序列为3.8%和1.7%。当用区域血流值进行归一化时，信号变化百分比的区域差异显著减小。引入了去卷积分析来模拟fMRI信号与呼气末二氧化碳水平之间的关系。从该分析中得出了诸如平均通过时间等时间参数，表明白质的反应比灰质区域慢。得出的结论是，fMRI反应幅度的差异很大程度上可归因于血流差异，并且灰质和白质之间的反应时间过程存在相当大的差异。
