Driver Ian D, Chiarelli Antonio Maria, Chandler Hannah L, Thomas Hannah, Manolova Svetla, Lu Hanzhang, Wise Richard G, Germuska Michael
Cardiff University Brain Research Imaging Centre (CUBRIC), School of Physics and Astronomy, Cardiff University, Cardiff, United Kingdom.
Cardiff University Brain Research Imaging Centre (CUBRIC), School of Psychology, Cardiff University, Cardiff, United Kingdom.
Imaging Neurosci (Camb). 2024 Sep 23;2. doi: 10.1162/imag_a_00298. eCollection 2024.
We previously introduced a calibrated fMRI framework that utilises respiratory modulation with only a single gas (CO) to map the grey matter (GM) cerebral metabolic rate of oxygen consumption (CMRO). The method decouples and estimates the cerebral blood volume (CBV) and the oxygen extraction fraction (OEF) from a single measure of the maximum BOLD modulation. The method links the two parameters of interest with a model of oxygen diffusion from capillaries to mitochondria which incorporates the cerebral blood flow (CBF). Here, we apply this framework to gas-free breath-hold calibrated fMRI (bhc-fMRI), where simultaneous BOLD and ASL acquisitions are combined with modulation of arterial COthrough repeated breath-holding. The accuracy and repeatability of the method is assessed in 33 healthy volunteers at rest and during continuous visual stimulation. Average GM OEF estimated from bhc-fMRI was 0.37 ± 0.04, indicating a small bias of 0.04 (with limits of agreement from -0.11 to 0.12) compared to the whole brain OEF of 0.32 ± 0.07 estimated from sagittal sinus using T2 Relaxation Under Spin Tagging (TRUST). The within-session repeatability of GM estimates were moderate to good for OEF, with ICC = 0.75 (0.56-0.87) and good to excellent for CMRO, with ICC = 0.88 (0.74-0.94). An ROI analysis in the visual cortex found an average CBF increase of 16%, a CMROincrease of 12%, and an OEF decrease of 3% during the visual stimulation. The bhc-fMRI measurement of CMROis simple to implement, has comparable accuracy and repeatability to existing gas-based methods, and is sensitive to modulations in metabolism during functional hyperaemia.
我们之前介绍了一种校准功能磁共振成像（fMRI）框架，该框架利用仅一种气体（一氧化碳）的呼吸调制来绘制灰质（GM）的脑氧代谢率（CMRO₂）。该方法从最大血氧水平依赖（BOLD）调制的单一测量中解耦并估计脑血容量（CBV）和氧提取分数（OEF）。该方法通过一个从毛细血管到线粒体的氧扩散模型（该模型纳入了脑血流量（CBF））将两个感兴趣的参数联系起来。在此，我们将此框架应用于无气体屏气校准fMRI（bhc-fMRI），其中通过重复屏气将同时进行的BOLD和动脉自旋标记（ASL）采集与动脉血一氧化碳的调制相结合。在33名健康志愿者休息时和持续视觉刺激期间评估了该方法的准确性和可重复性。从bhc-fMRI估计的平均GM OEF为0.37±0.04，与使用自旋标记下的T2弛豫（TRUST）从矢状窦估计的全脑OEF 0.32±0.07相比，显示出0.04的小偏差（一致性界限为-0.11至0.12）。GM估计值在会话内的可重复性对于OEF为中等至良好，组内相关系数（ICC）=0.75（0.56 - 0.87），对于CMRO₂为良好至优秀，ICC = 0.88（0.74 - 0.94）。视觉皮层的感兴趣区域（ROI）分析发现，在视觉刺激期间，平均CBF增加16%，CMRO₂增加12%，OEF降低3%。bhc-fMRI对CMRO₂的测量易于实施，与现有的基于气体的方法具有相当的准确性和可重复性，并且对功能性充血期间的代谢调制敏感。
