Abstract：
Intravoxel incoherent motion (IVIM) MRI has emerged as a valuable technique for the assessment of tissue characteristics and perfusion. However, there is limited knowledge about the relationship between IVIM-derived measures and changes at the level of the vascular network. In this study, we investigated the potential use of IVIM MRI as a noninvasive tool for measuring changes in cerebral vascular density. Variations in quantitative immunohistochemical measurements of the vascular density across different regions in the rat brain (cortex, corpus callosum, hippocampus, thalamus, and hypothalamus) were related to the pseudo-diffusion coefficient D* and the flowing blood fraction f in healthy Wistar rats. We assessed whether region-wise differences in the vascular density are reflected by variations in the IVIM measurements and found a significant positive relationship with the pseudo-diffusion coefficient (p < 0.05, β = 0.24). The effect of cerebrovascular alterations, such as blood-brain barrier (BBB) disruption on the perfusion-related IVIM parameters, is not well understood. Therefore, we investigated the effect of BBB disruption on the IVIM measures in a rat model of metabolic and vascular comorbidities (ZSF1 obese rat) and assessed whether this affects the relationship between the cerebral vascular density and the noninvasive IVIM measurements. We observed increased vascular permeability without detecting any differences in diffusivity, suggesting that BBB leakage is present before changes in the tissue integrity. We observed no significant difference in the relationship between cerebral vascular density and the IVIM measurements in our model of comorbidities compared with healthy normotensive rats.
摘要：
体素内不相干运动（IVIM）MRI已成为评估组织特征和灌注的有价值的技术。然而,关于IVIM衍生的测量值与血管网水平变化之间的关系的知识有限.在这项研究中,我们调查了IVIMMRI作为测量脑血管密度变化的无创工具的潜在用途.大鼠大脑不同区域血管密度的定量免疫组织化学测量的变化（皮质，call体,海马体,丘脑,和下丘脑）与健康Wistar大鼠的伪扩散系数D*和流动血液分数f有关。我们评估了血管密度的逐区域差异是否由IVIM测量值的变化反映,并发现与伪扩散系数的显著正相关(p<0.05,β=0.24)。脑血管改变的影响，如血脑屏障（BBB）对灌注相关IVIM参数的破坏，不是很了解。因此,我们研究了代谢和血管合并症大鼠模型(ZSF1肥胖大鼠)中BBB破坏对IVIM测量值的影响,并评估了这是否影响脑血管密度和无创IVIM测量值之间的关系.我们观察到血管通透性增加，但没有检测到扩散率的任何差异，提示在组织完整性改变之前存在BBB渗漏。与健康的正常血压大鼠相比，在我们的合并症模型中，脑血管密度与IVIM测量值之间的关系没有显着差异。
