Posse S, Olthoff U, Weckesser M, Jäncke L, Müller-Gärtner H W, Dager S R
Institute of Medicine, Research Center Jülich GmbH, Germany.
AJNR Am J Neuroradiol. 1997 Oct;18(9):1763-70.
To quantitate the amplitude changes and temporal dynamics of regional functional MR imaging signals during voluntary hyperventilation using blood oxygen level-dependent contrast echo-planar imaging.
Seven male subjects were studied during voluntary hyperventilation (PetCO2 = 20 mm Hg) regulated by capnometry. Measurements were made on multisection echo-planar MR images obtained with parameters of 1000/66 (repetition time/echo time), flip angle of 30 degrees, and voxel size of 3 x 3 x 5 mm3. Sensitivity of the functional MR imaging signal to changes in PetCO2, time delays in relation to PetCO2 changes, and time constants of functional MR imaging signal changes were assessed on a region-by-region basis.
Within 20 seconds of starting hyperventilation, rapid and substantial decreases in the functional MR imaging signal (by as much as 10%) were measured in areas of gray matter, which were significantly greater than the modest changes observed in white matter. Regional-specific effects in areas of the frontal, occipital, and parietooccipital cortex were stronger than in subcortical regions or in the cerebellum. Signal decreases measured with functional MR imaging were significantly delayed with respect to the reduction in PetCO2. Apparent differences between regional time constants did not reach statistical significance.
Regional and gray-white matter differences in functional MR imaging signal changes during controlled hyperventilation may reflect differences in metabolic activity, vascular regulation, and/or capillary density. When measuring brain activation with functional MR imaging, arterial PCO2 differences due to unregulated respiration may confound interpretation of activation-related functional MR imaging signal changes.
使用血氧水平依赖对比回波平面成像技术，定量分析在自主过度通气期间区域功能磁共振成像信号的幅度变化和时间动态。
七名男性受试者在通过二氧化碳监测仪调节的自主过度通气（呼气末二氧化碳分压 = 20 mmHg）期间接受研究。在多层面回波平面磁共振图像上进行测量，图像参数为1000/66（重复时间/回波时间）、翻转角30度和体素大小3×3×5 mm³。在逐个区域的基础上评估功能磁共振成像信号对呼气末二氧化碳分压变化的敏感性、与呼气末二氧化碳分压变化相关的时间延迟以及功能磁共振成像信号变化的时间常数。
在开始过度通气的20秒内，灰质区域的功能磁共振成像信号迅速且大幅下降（高达10%），这明显大于白质中观察到的适度变化。额叶、枕叶和顶枕叶皮质区域的区域特异性效应比皮质下区域或小脑中更强。功能磁共振成像测量的信号下降相对于呼气末二氧化碳分压的降低明显延迟。区域时间常数之间的明显差异未达到统计学意义。
在控制性过度通气期间，功能磁共振成像信号变化中的区域和灰白质差异可能反映代谢活动、血管调节和/或毛细血管密度的差异。当使用功能磁共振成像测量脑激活时，由于呼吸不规律导致的动脉血二氧化碳分压差异可能会混淆与激活相关的功能磁共振成像信号变化的解释。
