大鼠脑在闪光刺激过程中的功能定量磁化率映射（fQSM）
Functional quantitative susceptibility mapping (fQSM) of rat brain during flashing light stimulation.
机构信息
Graduate Institute of Biomedical Electronics and Bioinformatics, National Taiwan University, Taipei 106, Taiwan; Interdisciplinary MRI/MRS Lab, Department of Electrical Engineering, National Taiwan University, Taipei 106, Taiwan; Molecular Imaging Center, National Taiwan University, Taipei 106, Taiwan.
Graduate Institute of Biomedical Electronics and Bioinformatics, National Taiwan University, Taipei 106, Taiwan; Interdisciplinary MRI/MRS Lab, Department of Electrical Engineering, National Taiwan University, Taipei 106, Taiwan; Molecular Imaging Center, National Taiwan University, Taipei 106, Taiwan.
出版信息
Neuroimage. 2021 Jun;233:117924. doi: 10.1016/j.neuroimage.2021.117924. Epub 2021 Mar 19.
Functional magnetic resonance imaging (fMRI) based on the blood oxygenation level-dependent (BOLD) contrast has become an indispensable tool in neuroscience. However, the BOLD signal is nonlocal, lacking quantitative measurement of oxygenation fluctuation. This preclinical study aimed to introduced functional quantitative susceptibility mapping (fQSM) to complement BOLD-fMRI to quantitatively assess the local susceptibility and venous oxygen saturation (SvO). Rats were subjected to a 5 Hz flashing light and the different inhaled oxygenation levels (30% and 100%) were used to observe the venous susceptibility to quantify SvO. Phase information was extracted to produce QSM, and the activation responses of magnitude (conventional BOLD) and the QSM time-series were analyzed. During light stimulation, the susceptibility change of fQSM was four times larger than the BOLD signal change in both inhalation oxygenation conditions. Moreover, the responses in the fQSM map were more restricted to the visual pathway, such as the lateral geniculate nucleus and superior colliculus, compared with the relatively diffuse distributions in the BOLD map. Also, the calibrated SvO was approximately 84% (88%) when the task was on, 83% (87%) when the task was off during 30% (and during 100%) oxygen inhalation. This is the first fQSM study in a small animal model and increases our understanding of fQSM in the brains of small animals. This study demonstrated the feasibility, sensitivity, and specificity of fQSM using light stimulus, as fQSM provides quantitative clues as well as localized information, complementing the defects of BOLD-fMRI. In addition to neural activity, fQSM also assesses SvO as supplementary information while BOLD-fMRI dose not. Accordingly, the fQSM technique could be a useful quantitative tool for functional studies, such as longitudinal follow up of neurodegenerative diseases, functional recovery after brain surgery, and negative BOLD studies.
基于血氧水平依赖（BOLD）对比的功能磁共振成像（fMRI）已成为神经科学中不可或缺的工具。然而，BOLD 信号是非局部的，缺乏对氧合波动的定量测量。本临床前研究旨在引入功能定量磁化率映射（fQSM）来补充 BOLD-fMRI，以定量评估局部磁化率和静脉血氧饱和度（SvO）。对大鼠进行 5 Hz 闪光刺激，并使用不同的吸入氧合水平（30%和 100%）来观察静脉磁化率以量化 SvO。提取相位信息以产生 QSM，并分析幅度（常规 BOLD）和 QSM 时序列的激活响应。在光刺激期间，fQSM 的磁化率变化是两种吸入氧合条件下 BOLD 信号变化的四倍。此外，与 BOLD 图中相对弥散的分布相比，fQSM 图中的响应更局限于视觉通路，例如外侧膝状体和上丘。此外，在 30%（和 100%）氧气吸入时，任务开启时 SvO 约为 84%（88%），任务关闭时 SvO 约为 83%（87%）。这是在小动物模型中进行的第一项 fQSM 研究，增加了我们对小动物大脑中 fQSM 的理解。这项研究表明，使用光刺激进行 fQSM 具有可行性、灵敏度和特异性，fQSM 提供了定量线索和局部信息，补充了 BOLD-fMRI 的缺陷。除了神经活动外，fQSM 还评估 SvO 作为补充信息，而 BOLD-fMRI 则没有。因此，fQSM 技术可能是功能研究的有用定量工具，例如神经退行性疾病的纵向随访、脑手术后的功能恢复和阴性 BOLD 研究。
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