C. J. Gorter Center for High Field MRI, Department of Radiology, Leiden University Medical Center, Leiden, The Netherlands.
Magn Reson Med. 2010 Aug;64(2):358-68. doi: 10.1002/mrm.22420.
In dynamic susceptibility contrast perfusion MRI, arterial input function (AIF) measurements using the phase of the MR signal are traditionally performed inside an artery. However, phase-based AIF selection is also feasible in tissue surrounding an artery such as the middle cerebral artery, which runs approximately perpendicular to B(0) since contrast agents also induce local field changes in tissue surrounding the artery. The aim of this study was to investigate whether phase-based AIF selection is better performed in tissue just outside the middle cerebral artery than inside the artery. Additionally, phase-based AIF selection was compared to magnitude-based AIF selection. Both issues were studied theoretically and using numerical simulations, producing results that were validated using phantom experiments. Finally, an in vivo experiment was performed to illustrate the feasibility of phase-based AIF selection. Three main findings are presented: first, phase-based AIF selections are better made in tissue outside the middle cerebral artery, rather than within the middle cerebral artery, since in the latter approach partial-volume effects affect the shape of the estimated AIF. Second, optimal locations for phase-based AIF selection are similar for different clinical dynamic susceptibility contrast MRI sequences. Third, phase-based AIF selection allows more locations in tissue to be chosen that show the correct AIF than does magnitude-based AIF selection.
在动态磁敏感对比灌注 MRI 中，传统上使用 MR 信号的相位进行动脉输入函数 (AIF) 测量是在动脉内部进行的。然而，基于相位的 AIF 选择在动脉周围的组织中也是可行的，例如大脑中动脉，由于对比剂也会在动脉周围的组织中引起局部磁场变化，因此大脑中动脉几乎垂直于 B(0)。本研究的目的是探讨基于相位的 AIF 选择是在大脑中动脉外部的组织中进行，还是在动脉内部进行效果更好。此外，还比较了基于相位的 AIF 选择和基于幅度的 AIF 选择。这两个问题都是从理论和数值模拟两个方面进行研究的，并用体模实验进行了验证。最后，进行了一项体内实验，以说明基于相位的 AIF 选择的可行性。提出了三个主要发现：首先，在大脑中动脉外部的组织中进行基于相位的 AIF 选择比在大脑中动脉内部进行更好，因为在后一种方法中，部分容积效应会影响估计的 AIF 的形状。其次，对于不同的临床动态磁敏感对比 MRI 序列，基于相位的 AIF 选择的最佳位置相似。第三，与基于幅度的 AIF 选择相比，基于相位的 AIF 选择允许在组织中选择更多显示正确 AIF 的位置。
