Modelling vascular reactivity to investigate the basis of the relationship between cerebral blood volume and flow under CO2 manipulation
Modelling vascular reactivity to investigate the basis of the relationship between cerebral blood volume and flow under CO2 manipulation
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DOI：
10.1016/j.neuroimage.2007.08.022
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发表时间：
2008-01-01
期刊：
影响因子：
5.7
通讯作者：
Jezzard, Peter
中科院分区：
文献类型：
--
作者：
Piechnik, Stefan K.;Chiarelli, Peter A.;Jezzard, Peter
脑血流量（f）和血管容积（v）的变化是绘制脑活动和代谢的主要兴趣，但它们之间的关系目前缺乏足够的理论基础。为了解决这一问题，我们考虑了三种模型：均匀反应管模型（M1）;包括被动动脉流入和静脉容量的M1扩展（M2）;以及由19个隔室组成的解剖学上更合理的模型（M3），代表了整个血管尺寸范围和各自的CO2反应性，来自文献数据。我们认为，M2不能被描述为一个简单的缩放管的法律，但任何偏离线性近似是可以忽略不计的狭窄的生理范围内遇到的实验。为了正确地表示经验观察到的总体v-f关系的斜率，反应床应构成总血管体积的约一半，因此包括毛细血管和/或静脉的显著部分。模型M3显示v-f关系的斜率在0.16和1.0之间的系统变化，取决于所考虑的血管室。当使用其他实验方法（如流速）作为替代测量时，这将进一步复杂化。该效应在微血管区室中特别大，但是当与较大血管平均时，在成像方法的典型条件下斜率的变化包含在0.25至0.55内。我们的结论是，v-f关系不是一个固定的函数，但形状和斜率取决于反应体积的组成和所使用的实验方法。(C)2007年爱思唯尔公司All rights reserved.
Changes in cerebral blood flow (f) and vascular volume (v) are of major interest in mapping cerebral activity and metabolism, but the relation between them currently lacks a sufficient theoretical basis. To address this we considered three models: a uniform reactive tube model (M1); an extension of M 1 that includes passive arterial inflow and venous volume (M2); and a more anatomically plausible model (M3) consisting of 19 compartments representing the whole range of vascular sizes and respective CO2 reactivities, derived from literature data. We rind that M2 cannot be described as the simple scaling of a tube law, but any divergence from a linear approximation is negligible within the narrow physiological range encountered experimentally. In order to represent correctly the empirically observed slope of the overall v-f relationship, the reactive bed should constitute about half of the total vascular volume, thus including a significant fraction of capillaries and/or veins. Model M3 demonstrates systematic variation of the slope of the v-f relationship between 0.16 and 1.0, depending on the vascular compartment under consideration. This is further complicated when other experimental approaches such as flow velocity are used as substitute measurements. The effect is particularly large in microvascular compartments, but when averaged with larger vessels the variations in slope are contained within 0.25 to 0.55 under conditions typical for imaging methods. We conclude that the v-f relationship is not a fixed function but that both the shape and slope depend on the composition of the reactive volume and the experimental methods used. (C) 2007 Elsevier Inc. All rights reserved.