Objective

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.

Material and methods

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.

Results

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⁻¹ mM⁻¹, for voxels identified as useful AIF candidate in ΔR2* images according to the conventional criteria.

Discussion

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.

中文翻译：

---

用于灌注成像的动态对比增强 QSM：血液和组织中 ΔR2*- 和基于 QSM 的对比剂浓度时间曲线的系统比较。

客观的

在动态磁化率对比 MRI (DSC-MRI) 中，需要动脉输入函数 (AIF) 来量化灌注。然而，根据幅度 MRI 信号数据估计造影剂 (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 会与其浓度成比例地改变磁化率。

材料与方法

根据与时间、形状和峰值浓度相关的常规标准选择具有合理外观的 AIF，从 Δ R 2* 和 QSM 图像中注册，并通过目视检查相互比较。Δ R 2*- 和基于 QSM 的 AIF 均用于基于来自 Δ R 2* 的组织浓度数据以及 QSM 图像的灌注计算。

结果

基于 Δ R 2* 和 QSM 数据的AIF显示出非常相似的形状，估计的脑血流量值和平均通过时间也相似。对于根据常规标准在Δ R 2* 图像中被识别为有用AIF候选的体素，对应的Δ R 2* 与基于QSM的浓度估计的分析产生89 s ^-1  mM ^-1的横向弛豫估计。

讨论

有趣的是，对于标准的 DSC-MRI 实验，基于 Δ R 2* 与 QSM 数据的动脉浓度时间曲线在形状上通常非常相似，并且在代表血液的体素中获得的弛豫与在先前研究中获得的组织弛豫相似。