Arterial Spin Labeling

As noted above, the fMRI BOLD signal indirectly reflects relative changes in neural activity because it is based on interacting changes in neurovascular function and oxygen concentration. In this way, measuring the BOLD signal has at least one disadvantage compared with PET; namely, it provides a surrogate and nonquantitative parameter of neurophysiological activity. However, using specialiZed MRI scanning parameters (referred to as pulse sequences), the quantitative parameter, rCBF, can be estimated with a technique called perfusion imaging, which relies on arterial spin labeling (Detre and Wang, 2002). This technique is gaining increasing use in the field of neuroimaging, and as reviewed by the complementary chapter on neuroimaging in this volume, it has been applied recently in behavioral medicine studies of cardiovascular and neuroendocrine stress reactivity (Gianaros et al, 2009; Wang et al, 2005, 2007). Hence, perfusion MRI is an emerging non-invasive method that may better capture quantitative changes in cerebral blood flow that are more closely related to neural activity and metabolism patterns.

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