Department of Medical Radiation Physics, Lund University, Barngatan 4, 22185, Lund, Sweden.
Russell H. Morgan Department of Radiology and Radiological Science, Johns Hopkins University School of Medicine, Baltimore, MD, USA.
MAGMA. 2020 Oct;33(5):663-676. doi: 10.1007/s10334-020-00831-x. Epub 2020 Feb 20.
In dynamic susceptibility contrast MRI (DSC-MRI), an arterial input function (AIF) is required to quantify perfusion. However, estimation of the concentration of contrast agent (CA) from magnitude MRI signal data is challenging. A reasonable alternative would be to quantify CA concentration using quantitative susceptibility mapping (QSM), as the CA alters the magnetic susceptibility in proportion to its concentration.
AIFs with reasonable appearance, selected on the basis of conventional criteria related to timing, shape, and peak concentration, were registered from both ΔR2* and QSM images and mutually compared by visual inspection. Both ΔR2*- and QSM-based AIFs were used for perfusion calculations based on tissue concentration data from ΔR2*as well as QSM images.
AIFs based on ΔR2* and QSM data showed very similar shapes and the estimated cerebral blood flow values and mean transit times were similar. Analysis of corresponding ΔR2* versus QSM-based concentration estimates yielded a transverse relaxivity estimate of 89 s mM, for voxels identified as useful AIF candidate in ΔR2* images according to the conventional criteria.
Interestingly, arterial concentration time curves based on ΔR2* versus QSM data, for a standard DSC-MRI experiment, were generally very similar in shape, and the relaxivity obtained in voxels representing blood was similar to tissue relaxivity obtained in previous studies.
在动态对比磁共振成像（DSC-MRI）中，需要动脉输入函数（AIF）来量化灌注。然而，从幅度 MRI 信号数据估计对比剂（CA）的浓度具有挑战性。一个合理的替代方法是使用定量磁化率映射（QSM）来量化 CA 浓度，因为 CA 会根据其浓度按比例改变磁化率。
根据与时间、形状和峰值浓度相关的常规标准，从 ΔR2和 QSM 图像中选择外观合理的 AIF，并通过目视检查相互比较。基于 ΔR2和 QSM 的 AIF 都用于基于组织浓度数据从 ΔR2*和 QSM 图像进行灌注计算。
基于 ΔR2和 QSM 数据的 AIF 形状非常相似，估计的脑血流量值和平均通过时间相似。对相应的 ΔR2与基于 QSM 的浓度估计进行分析，得出根据常规标准在 ΔR2*图像中识别为有用 AIF 候选的体素的横向弛豫率估计值为 89 s mM。
有趣的是，根据标准 DSC-MRI 实验，基于 ΔR2*与 QSM 数据的动脉浓度时间曲线在形状上通常非常相似，并且代表血液的体素中的弛豫率与之前研究中获得的组织弛豫率相似。
