Breath-hold BOLD fMRI without CO2 sampling enables estimation of venous cerebral blood volume: potential use in normalization of stimulus-evoked BOLD fMRI data
Breath-hold BOLD fMRI without CO2 sampling enables estimation of venous cerebral blood volume: potential use in normalization of stimulus-evoked BOLD fMRI data
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DOI：
10.1016/j.neuroimage.2023.120492
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发表时间：
2023-12-09
期刊：
影响因子：
5.7
通讯作者：
Wise，Richard G.
中科院分区：
文献类型：
--
作者：
Biondetti，Emma;Chiarelli，Antonio Maria;Wise，Richard G.
BOLD fMRI信号已与血管舒张刺激联合使用，作为脑血管反应性（CVR）的标志物：由血管舒张刺激的单位变化引起的脑血流量（CBF）的相对变化。通过数值模拟，我们证明了血管舒张引起的相对BOLD信号变化的变异性受到含脱氧血红蛋白脑血容量（CBV）变异性的强烈影响，因为这种变异性的来源可能比CVR更突出。因此，将等代谢血管舒张引起的相对BOLD信号变化描述为脱氧CBV （CBVdHb）而不是CVR可能更合适。考虑到这一点，我们实施了一种新的方法来绘制CBVdHb标记物，称为BOLD- cbv，该方法基于体素方向BOLD信号变化的归一化，通过估计来自充满静脉血的体素的血管内静脉BOLD信号。在27名健康志愿者的队列中，从上矢状窦提取了重复呼吸期间记录的血管内静脉BOLD信号变化，并将其用作全脑的回归因子，得出BOLD- cbv图。在同一队列中，我们通过比较各组BOLD- cbv对视觉运动学习任务的反应，以及BOLD- cbv的体素方向血管协变量和大潮末二氧化碳（BOLD- cvr）每mmHg变化的BOLD信号变化，证明了BOLD- cbv在刺激诱发的BOLD功能磁共振归一化中的潜在应用。在运动任务诱导的BOLD反应中，BOLD- cbv的经验测量比BOLD- cvr从潮末二氧化碳记录中估计的更多。新方法可以通过测量血管特征来潜在地增加群体功能磁共振成像研究的能力，并且与传统方法估算BOLD-CVR不同，它具有不需要实验测量潮末二氧化碳的强大实用优势。它也比BOLD-CVR更能代表脑血管系统的特定生理特征，即血容量。
BOLD fMRI signal has been used in conjunction with vasodilatory stimulation as a marker of cerebrovascular reactivity (CVR): the relative change in cerebral blood flow (CBF) arising from a unit change in the vasodilatory stimulus. Using numerical simulations, we demonstrate that the variability in the relative BOLD signal change induced by vasodilation is strongly influenced by the variability in deoxyhemoglobin-containing cerebral blood volume (CBV), as this source of variability is likely to be more prominent than that of CVR. It may, therefore, be more appropriate to describe the relative BOLD signal change induced by an isometabolic vasodilation as a proxy of deoxygenated CBV (CBVdHb) rather than CVR. With this in mind, a new method was implemented to map a marker of CBVdHb, termed BOLD-CBV, based on the normalization of voxel-wise BOLD signal variation by an estimate of the intravascular venous BOLD signal from voxels filled with venous blood. The intravascular venous BOLD signal variation, recorded during repeated breath-holding, was extracted from the superior sagittal sinus in a cohort of 27 healthy volunteers and used as a regressor across the whole brain, yielding maps of BOLD-CBV. In the same cohort, we demonstrated the potential use of BOLD-CBV for the normalization of stimulus-evoked BOLD fMRI by comparing group-level BOLD fMRI responses to a visuomotor learning task with and without the inclusion of voxel-wise vascular covariates of BOLD-CBV and the BOLD signal change per mmHg variation in end-tidal carbon dioxide (BOLD-CVR). The empirical measure of BOLD-CBV accounted for more between-subject variability in the motor task-induced BOLD responses than BOLD-CVR estimated from end-tidal carbon dioxide recordings. The new method can potentially increase the power of group fMRI studies by including a measure of vascular characteristics and has the strong practical advantage of not requiring experimental measurement of end-tidal carbon dioxide, unlike traditional methods to estimate BOLD-CVR. It also more closely represents a specific physiological characteristic of brain vasculature than BOLD-CVR, namely blood volume.