A general analysis of calibrated BOLD methodology for measuring CMRO2 responses: Comparison of a new approach with existing methods
A general analysis of calibrated BOLD methodology for measuring CMRO2 responses: Comparison of a new approach with existing methods
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DOI：
10.1016/j.neuroimage.2011.11.081
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发表时间：
2012-03-01
期刊：
影响因子：
5.7
通讯作者：
Buxton, Richard B.
中科院分区：
文献类型：
--
作者：
Blockley, Nicholas P.;Griffeth, Valerie E. M.;Buxton, Richard B.
BOLD 对刺激的反应幅度不仅取决于脑血流量 (CBF) 和氧代谢 (CMRO2) 的变化，还取决于血细胞比容、氧提取分数 (OEF) 和血容量等基线生理参数。校准 BOLD 方法旨在通过执行额外的校准扫描来解释这种生理变化。尽管我们建议测量可逆横向弛豫率，但这种校准通常包括高碳酸血症或高氧呼吸挑战。也可以使用R-2'。 BOLD 效应的详细模型用于模拟每个校准实验以及激活实验，同时改变与基线状态和激活响应相关的许多生理参数。通过测试由校准参数结合测量的 CBF 缩放的 BOLD 对激活的响应是否提供了足够的信息来可靠地区分不同水平的 CMRO2 响应（尽管存在潜在的生理变异性），从而考虑了不同校准方法的有效性。此外，还测试了每种技术的基本假设中的不准确性的影响，例如高碳酸血症期间的同代谢。该研究的三个主要发现是： 1）基于 R-2' 的新校准方法效果相当好，尽管不如理想的高碳酸血症方法； 2）高氧校准方法明显较差，因为必须假设基线血细胞比容和OEF，而这些生理参数对测量有显着影响； 3）激活时静脉血量的变化是所有方法的一个重要混杂变量，当不确定时，高碳酸血症方法是最稳健的。 (C) 2011 Elsevier Inc. 保留所有权利。
The amplitude of the BOLD response to a stimulus is not only determined by changes in cerebral blood flow (CBF) and oxygen metabolism (CMRO2), but also by baseline physiological parameters such as haematocrit, oxygen extraction fraction (OEF) and blood volume. The calibrated BOLD approach aims to account for this physiological variation by performing an additional calibration scan. This calibration typically consists of a hypercapnia or hyperoxia respiratory challenge, although we propose that a measurement of the reversible transverse relaxation rate. R-2', might also be used. A detailed model of the BOLD effect was used to simulate each of the calibration experiments, as well as the activation experiment, whilst varying a number of physiological parameters associated with the baseline state and response to activation. The effectiveness of the different calibration methods was considered by testing whether the BOLD response to activation scaled by the calibration parameter combined with the measured CBF provides sufficient information to reliably distinguish different levels of CMRO2 response despite underlying physiological variability. In addition the effect of inaccuracies in the underlying assumptions of each technique were tested, e.g. isometabolism during hypercapnia.The three primary findings of the study were: 1) The new calibration method based on R-2' worked reasonably well, although not as well as the ideal hypercapnia method; 2) The hyperoxia calibration method was significantly worse because baseline haematocrit and OEF must be assumed, and these physiological parameters have a significant effect on the measurements; and 3) the venous blood volume change with activation is an important confounding variable for all of the methods, with the hypercapnia method being the most robust when this is uncertain. (C) 2011 Elsevier Inc. All rights reserved.