A novel perspective to calibrate temporal delays in cerebrovascular reactivity using hypercapnic and hyperoxic respiratory challenges
A novel perspective to calibrate temporal delays in cerebrovascular reactivity using hypercapnic and hyperoxic respiratory challenges
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DOI：
10.1016/j.neuroimage.2017.11.044
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发表时间：
2019-02-15
期刊：
影响因子：
5.7
通讯作者：
Cook, Douglas J.
中科院分区：
文献类型：
--
作者：
Champagne, Allen A.;Bhogal, Alex A.;Cook, Douglas J.
血流量在不同脑区的重新分布，由高碳酸血症的血管活性性质引起，在检查脑血管反应性（CVR）反应延迟时可能会引入错误。在这项研究中，我们提出了一种新的分析方法来表征血液动力学延迟的血氧水平依赖（BOLD）反应高碳酸血症，高氧，作为一种方式来提供洞察大脑皮层区域之间的血管反应性的瞬态差异，并在整个组织深度。采用伪连续动脉自旋标记序列在19名健康成人（12名女性; 20 +/- 2岁）中同时采集BOLD和脑血流量。尽管在高碳酸血症诱导的反应延迟时间上显示出明显的差异（P < 0.05; Bonferroni校正），但一旦使用非血管活性高氧气体激发导出的推注到达时间进行校准，灰质区域显示出均匀的血流动力学延迟（P > 0.05）。随着白色组织深度的增加，观察到更长的高碳酸血症时间延迟，尽管在组织深度或灰质和白色组织之间的高氧期间没有发现反应延迟的显着差异。此外，使用高氧校准高碳酸血症延迟显示，更深的白色物质层可能更容易发生血流的动态重新分布，这在健康受试者中引入了1至3 s的反应滞后时间。这些结果表明，高碳酸和高氧气体吸入MRI的组合可用于区分CVR的差异，这些差异是由于刺激到达时间延迟（由于血管系统的局部结构）或优先血流分布引起的。对高碳酸血症的校准反应延迟提供了对脑血管生理学的重要见解，并且可用于校正与血管损伤相关的反应延迟。
Redistribution of blood flow across different brain regions, arising from the vasoactive nature of hypercapnia, can introduce errors when examining cerebrovascular reactivity (CVR) response delays. In this study, we propose a novel analysis method to characterize hemodynamic delays in the blood oxygen level dependent (BOLD) response to hypercapnia, and hyperoxia, as a way to provide insight into transient differences in vascular reactivity between cortical regions, and across tissue depths. A pseudo-continuous arterial spin labeling sequence was used to acquire BOLD and cerebral blood flow simultaneously in 19 healthy adults (12 F; 20 +/- 2 years) during boxcar CO2 and O-2 gas inhalation paradigms. Despite showing distinct differences in hypercapnia-induced response delay times (P < 0.05; Bonferroni corrected), grey matter regions showed homogenous hemodynamic latencies (P > 0.05) once calibrated for bolus arrival time derived using non-vasoactive hyperoxic gas challenges. Longer hypercapnic temporal delays were observed as the depth of the white matter tissue increased, although no significant differences in response lag were found during hyperoxia across tissue depth, or between grey and white matter. Furthermore, calibration of hypercapnic delays using hyperoxia revealed that deeper white matter layers may be more prone to dynamic redistribution of blood flow, which introduces response lag times ranging between 1 and 3 s in healthy subjects. These findings suggest that the combination of hypercapnic and hyperoxic gas-inhalation MRI can be used to distinguish between differences in CVR that arise as a result of delayed stimulus arrival time (due to the local architecture of the cerebrovasculature), or preferential blood flow distribution. Calibrated response delays to hypercapnia provide important insights into cerebrovascular physiology, and may be used to correct response delays associated with vascular impairment.