Mouridsen Kim, Hansen Mikkel Bo, Østergaard Leif, Jespersen Sune Nørhøj
Center of Functionally Integrative Neuroscience and MINDLab, Institute of Clinical Medicine, Aarhus University, Aarhus, Denmark.
1] Center of Functionally Integrative Neuroscience and MINDLab, Institute of Clinical Medicine, Aarhus University, Aarhus, Denmark [2] Department of Neuroradiology, Aarhus University Hospital, Aarhus, Denmark.
J Cereb Blood Flow Metab. 2014 Sep;34(9):1511-21. doi: 10.1038/jcbfm.2014.111. Epub 2014 Jun 18.
The regional availability of oxygen in brain tissue is traditionally inferred from the magnitude of cerebral blood flow (CBF) and the concentration of oxygen in arterial blood. Measurements of CBF are therefore widely used in the localization of neuronal response to stimulation and in the evaluation of patients suspected of acute ischemic stroke or flow-limiting carotid stenosis. It was recently demonstrated that capillary transit time heterogeneity (CTH) limits maximum oxygen extraction fraction (OEF(max)) that can be achieved for a given CBF. Here we present a statistical approach for determining CTH, mean transit time (MTT), and CBF using dynamic susceptibility contrast magnetic resonance imaging (DSC-MRI). Using numerical simulations, we demonstrate that CTH, MTT, and OEF(max) can be estimated with low bias and variance across a wide range of microvascular flow patterns, even at modest signal-to-noise ratios. Mean transit time estimated by singular value decomposition (SVD) deconvolution, however, is confounded by CTH. The proposed technique readily identifies malperfused tissue in acute stroke patients and appears to highlight information not detected by the standard SVD technique. We speculate that this technique permits the non-invasive detection of tissue with impaired oxygen delivery in neurologic disorders such as acute ischemic stroke and Alzheimer's disease during routine diagnostic imaging.
传统上，脑组织中局部氧的可利用性是根据脑血流量（CBF）的大小和动脉血中的氧浓度推断出来的。因此，CBF测量被广泛用于神经元对刺激反应的定位以及对疑似急性缺血性中风或血流受限性颈动脉狭窄患者的评估。最近有研究表明，毛细血管通过时间异质性（CTH）限制了在给定CBF条件下所能达到的最大氧摄取分数（OEF(max)）。在此，我们提出一种利用动态磁敏感对比磁共振成像（DSC-MRI）来确定CTH、平均通过时间（MTT）和CBF的统计方法。通过数值模拟，我们证明，即使在适度的信噪比下，在广泛的微血管血流模式范围内，CTH、MTT和OEF(max)都能以低偏差和低方差进行估计。然而，通过奇异值分解（SVD）反卷积估计的平均通过时间会受到CTH的干扰。所提出的技术能够轻易识别急性中风患者的灌注不良组织，并且似乎能突出标准SVD技术未检测到的信息。我们推测，在常规诊断成像过程中，该技术能够对诸如急性缺血性中风和阿尔茨海默病等神经系统疾病中氧输送受损的组织进行无创检测。
