Department of Radiology, CJ Gorter Center for High Field MRI, Leiden University Medical Center, Leiden, The Netherlands.
Magn Reson Med. 2012 May;67(5):1324-31. doi: 10.1002/mrm.23120. Epub 2011 Aug 16.
Correct arterial input function (AIF) measurements in dynamic susceptibility contrast-MRI are crucial for quantification of the hemodynamic parameters. Often a single global AIF is selected near a large brain-feeding artery. Alternatively, local AIF measurements aim for voxel-specific AIFs from smaller arteries. Because local AIFs are measured higher in the arterial-tree, it is assumed that these will reflect the true input of the microvasculature much better. However, do the measured local AIFs reflect the true concentration-time curves of small arteries? To answer this question, in vivo data were used to evaluate local AIF candidates selected based on two different types of angiograms. For interpretation purposes, a 3D numerical model that simulated partial-volume effects in local AIF measurements was created and the simulated local AIFs were compared to the ground truth. The findings are 2-fold. First, the in vivo data showed that the shape-characteristics of local AIFs are similar to the shape-characteristics of gray matter concentration-time curves. Second, these findings are supported by the simulations showing broadening of the measured local AIFs compared to the ground truth. These findings are suggesting that local AIF measurements do not necessarily reflect the true concentration-time curve in small arteries.
准确的动脉输入函数（AIF）测量在动态对比磁共振成像中对于量化血流动力学参数至关重要。通常在靠近大脑供血动脉的位置选择一个单一的全局 AIF。或者，局部 AIF 测量旨在从小动脉获得特定体素的 AIF。由于局部 AIF 在动脉树中测量得更高，因此假设这些 AIF 能更好地反映微血管的真实输入情况。然而，所测量的局部 AIF 是否能反映小动脉的真实浓度-时间曲线呢？为了回答这个问题，我们使用体内数据来评估基于两种不同类型血管造影的局部 AIF 候选物。为了便于解释，我们创建了一个 3D 数值模型，模拟了局部 AIF 测量中的部分容积效应，并将模拟的局部 AIF 与真实情况进行了比较。结果有两个方面。首先，体内数据表明，局部 AIF 的形状特征与灰质浓度-时间曲线的形状特征相似。其次，模拟结果显示，与真实情况相比，测量的局部 AIF 会变宽，这也支持了这些发现。这些结果表明，局部 AIF 测量不一定能反映小动脉的真实浓度-时间曲线。
