人类层流 fMRI 的非 BOLD 对比：CBF、CBV 和 CMR O2,NeuroImage

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人类层流 fMRI 的非 BOLD 对比：CBF、CBV 和 CMR O2
NeuroImage ( IF 4.7 ) Pub Date : 2019-08-01 , DOI: 10.1016/j.neuroimage.2017.07.041
Laurentius Huber ₁ , Kâmil Uludağ ₂ , Harald E Möller ₃

Affiliation

使用血氧水平依赖性 (BOLD) 对比的功能磁共振成像 (fMRI) 通过诱发脑血流量 (CBF)、脑血容量 (CBV) 和脑氧代谢率 (CMRO2) 的变化间接探测神经元活动的变化。梯度回波 BOLD 信号主要对组织中的升静脉和软膜静脉敏感。因此，对神经元激活可实现的空间特异性是有限的。此外，CBF、CBV 和 CMRO2 的非线性相互作用会妨碍对具有不同基线生理学的皮层深度的 BOLD 信号的定量解释。直接在深度相关水平上测量 CBF、CBV 或 CMRO2 有可能克服这些限制。这里，我们回顾了这些生理学明确对比的候选者，特别关注动脉自旋标记 (ASL)、血管空间占用 (VASO) 和校准 fMRI。这些方法在 fMRI 序列参数空间和人类神经科学研究的适用性方面进行了审查。我们展示了人类中深度依赖的“非 BOLD-fMRI”及其时空特征的代表性结果。我们得出的结论是，与传统 fMRI 相比，非 BOLD 方法是有前景的替代方法，因为它们可以提供更好的空间特异性、可量化性，因此，作为皮质深度函数的生理可解释性。然而，在具有固有低信噪比 (SNR) 的亚毫米分辨率下，它们的使用仍然具有挑战性。尽管如此，我们认为“非 BOLD-fMRI”

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Non-BOLD contrast for laminar fMRI in humans: CBF, CBV, and CMR O2

Functional magnetic resonance imaging (fMRI) using the blood oxygenation level-dependent (BOLD) contrast indirectly probes neuronal activity changes via evoked cerebral blood flow (CBF), cerebral blood volume (CBV) and cerebral metabolic rate of oxygen (CMRO2) changes. The gradient-echo BOLD signal is mostly sensitive to ascending veins in the tissue and to pial veins. Thereby, the achievable spatial specificity to neuronal activation is limited. Furthermore, the non-linear interaction of CBF, CBV and CMRO2 can hamper quantitative interpretations of the BOLD signal across cortical depths with different baseline physiology. Measuring CBF, CBV or CMRO2 directly on a depth-dependent level has the potential to overcome these limitations. Here, we review these candidates of physiologically well-defined contrasts with the particular focus on arterial spin labeling (ASL), vascular space occupancy (VASO) and calibrated fMRI. These methods are reviewed with respect to their fMRI sequence parameter space and the applicability for neuroscientific studies in humans. We show representative results of depth-dependent 'non-BOLD-fMRI' in humans and their spatiotemporal characteristics. We conclude that non-BOLD methods are promising alternatives compared to conventional fMRI as they can provide improved spatial specificity, quantifiability and, hence, physiological interpretability as a function of cortical depth. At submillimeter resolution with inherently low signal-to-noise ratio (SNR), however, their use is still challenging. Nevertheless, we believe that 'non-BOLD-fMRI' is a useful alternative for depth-dependent investigations, by providing valuable insights into neurovascular coupling models that facilitate the interpretability of fMRI for neuroscientific applications.

更新日期：2019-08-01

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