Department of Radiology, Stanford University, Stanford, California 94305-5488, USA.
Magn Reson Med. 2010 Jun;63(6):1548-56. doi: 10.1002/mrm.22329.
Dynamic susceptibility contrast (DSC) and arterial spin labeling (ASL) are both used to measure cerebral blood flow (CBF), but neither technique is ideal. Absolute DSC-CBF quantitation is challenging due to many uncertainties, including partial- volume errors and nonlinear contrast relaxivity. ASL can measure quantitative CBF in regions with rapidly arriving flow, but CBF is underestimated in regions with delayed arrival. To address both problems, we have derived a patient-specific correction factor, the ratio of ASL- and DSC-CBF, calculated only in short-arrival-time regions (as determined by the DSC-based normalized bolus arrival time [Tmax]). We have compared the combined CBF method to gold-standard xenon CT in 20 patients with cerebrovascular disease, using a range of Tmax threshold levels. Combined ASL and DSC CBF demonstrated quantitative accuracy as good as the ASL technique but with improved correlation in voxels with long Tmax. The ratio of MRI-based CBF to xenon CT CBF (coefficient of variation) was 90 +/- 30% (33%) for combined ASL and DSC CBF, 43 +/- 21% (47%) for DSC, and 91 +/- 31% (34%) for ASL (Tmax threshold 3 sec). These findings suggest that combining ASL and DSC perfusion measurements improves quantitative CBF measurements in patients with cerebrovascular disease.
动态对比磁共振成像（DSC）和动脉自旋标记（ASL）均可用于测量脑血流（CBF），但两种技术都不完美。绝对 DSC-CBF 定量存在许多不确定性，包括部分容积效应和非线性对比弛豫率，因此具有挑战性。ASL 可测量快速到达区域的定量 CBF，但在到达延迟的区域 CBF 会被低估。为了解决这两个问题，我们推导了一种患者特异性校正因子，即 ASL 和 DSC-CBF 的比值，仅在短到达时间区域（由 DSC 基于归一化的对比剂到达时间 Tmax 确定）进行计算。我们在 20 例脑血管病患者中比较了联合 CBF 方法与金标准氙 CT，使用了一系列 Tmax 阈值水平。在 Tmax 较长的体素中，联合 ASL 和 DSC CBF 表现出与 ASL 技术一样好的定量准确性，但相关性更好。基于 MRI 的 CBF 与氙 CT CBF 的比值（变异系数）分别为联合 ASL 和 DSC CBF 的 90% ± 30%（33%）、DSC 的 43% ± 21%（47%）和 ASL 的 91% ± 31%（34%）（Tmax 阈值 3 秒）。这些发现表明，联合 ASL 和 DSC 灌注测量可改善脑血管病患者的定量 CBF 测量。
