Detrimental effects of BOLD signal in arterial spin Labeling fMRI at high field strength
Detrimental effects of BOLD signal in arterial spin Labeling fMRI at high field strength
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DOI：
10.1002/mrm.20976
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发表时间：
2006-09-01
影响因子：
3.3
通讯作者：
van Zijl, Peter C. M.
中科院分区：
文献类型：
--
作者：
Lu, Hanzhang;Donahue, Manus J.;van Zijl, Peter C. M.
动脉自旋标记（ASL）MRI是一种无创测量脑血流量（CBF）的有用技术。高场强为ASL提供了独特的优势，因为血液T-1弛豫时间较长，使这项技术成为一种有前途的定量方法，用于功能性脑映射。然而，更高的磁场也带来了新的挑战。在这里，它表明，在3.0 T的ASL功能性MRI（fMRI）确定的CBF响应包含显着的污染，从血氧水平依赖性（BOLD）的影响。由于标签和对照图像的交错采集，这两次扫描之间的血氧状态差异可能导致图像相减时静态信号的不完全消除，导致估计的CBF血液动力学中的BOLD相关伪影。如果不考虑，这种影响可能会使ASL结果的解释复杂化，例如，导致反应的延迟开始和偏移，或诱导人为的刺激后下冲。BOLD的贡献也降低了基于ASL的fMRI的灵敏度。提出了校正方法以减少伪影，增加激活体素的数量（18 +/-5%，P = 0.006）和更准确地估计CBF时间特征。
Arterial spin labeling (ASL) MRI is a useful technique for noninvasive measurement of cerebral blood flow (CBF) in humans. High field strength provides a unique advantage for ASL because of longer blood T-1 relaxation times, making this technique a promising quantitative approach for functional brain mapping. However, higher magnetic field also introduces new challenges. Here it is shown that the CBF response determined using ASL functional MRI (fMRI) at 3.0 T contains significant contamination from blood-oxygenation-level-dependent (BOLD) effects. Due to interleaved acquisitions of label and control images, difference in blood oxygenation status between these two scans can cause incomplete cancellation of the static signal upon image subtraction, resulting in a BOLD-related artifact in the estimated CBF hemodynamics. If not accounted for, such an effect can complicate the interpretation of the ASL results, e.g., causing a delayed onset and offset of the response, or inducing an artifactual poststimulus undershoot. The BOLD contribution also decreases the sensitivity of ASL-based fMRI. Correction methods are proposed to reduce the artifact, giving increased number of activated voxels (18 +/- 5%, P = 0.006) and more accurate estimation of CBF temporal characteristics.