Englund Erin K, Langham Michael C
Department of Orthopaedic Surgery, University of California, San Diego, La Jolla, CA, United States.
Department of Radiology, University of Pennsylvania, Philadelphia, PA, United States.
Front Physiol. 2020 Feb 28;11:120. doi: 10.3389/fphys.2020.00120. eCollection 2020.
The endothelium regulates and mediates vascular homeostasis, allowing for dynamic changes of blood flow in response to mechanical and chemical stimuli. Endothelial dysfunction underlies many diseases and is purported to be the earliest pathologic change in the progression of atherosclerotic disease. Peripheral vascular function can be interrogated by measuring the response kinetics following induced ischemia or exercise. In the presence of endothelial dysfunction, there is a blunting and delay of the hyperemic response, which can be measured non-invasively using a variety of quantitative magnetic resonance imaging (MRI) methods. In this review, we summarize recent developments in non-contrast, proton MRI for dynamic quantification of blood flow and oxygenation. Methodologic description is provided for: blood oxygenation-level dependent (BOLD) signal that reflect combined effect of blood flow and capillary bed oxygen content; arterial spin labeling (ASL) for quantification of regional perfusion; phase contrast (PC) to quantify arterial flow waveforms and macrovascular blood flow velocity and rate; high-resolution MRI for luminal flow-mediated dilation; and dynamic MR oximetry to quantify oxygen saturation. Overall, results suggest that these dynamic and quantitative MRI methods can detect endothelial dysfunction both in the presence of overt cardiovascular disease (such as in patients with peripheral artery disease), as well as in sub-clinical settings (i.e., in chronic smokers, non-smokers exposed to e-cigarette aerosol, and as a function of age). Thus far, these tools have been relegated to the realm of research, used as biomarkers of disease progression and therapeutic response. With proper validation, MRI-measures of vascular function may ultimately be used to complement the standard clinical workup, providing additional insight into the optimal treatment strategy and evaluation of treatment efficacy.
内皮细胞调节并介导血管稳态，使血流能够根据机械和化学刺激做出动态变化。内皮功能障碍是许多疾病的基础，被认为是动脉粥样硬化疾病进展中最早出现的病理变化。可通过测量诱导性缺血或运动后的反应动力学来评估外周血管功能。在内皮功能障碍的情况下，充血反应会减弱和延迟，这可以使用多种定量磁共振成像（MRI）方法进行无创测量。在本综述中，我们总结了非对比质子MRI在血流和氧合动态定量方面的最新进展。文中提供了以下方法的描述：反映血流和毛细血管床氧含量综合作用的血氧水平依赖（BOLD）信号；用于区域灌注定量的动脉自旋标记（ASL）；用于量化动脉血流波形以及大血管血流速度和速率的相位对比（PC）；用于管腔血流介导的扩张的高分辨率MRI；以及用于量化氧饱和度的动态磁共振血氧测定法。总体而言，结果表明这些动态和定量MRI方法既能在存在明显心血管疾病的情况下（如外周动脉疾病患者）检测到内皮功能障碍，也能在亚临床环境中（即慢性吸烟者、接触电子烟烟雾的非吸烟者以及作为年龄的函数）检测到。到目前为止，这些工具仍局限于研究领域，用作疾病进展和治疗反应的生物标志物。经过适当验证后，MRI测量的血管功能最终可能用于补充标准临床检查，为最佳治疗策略和治疗效果评估提供更多见解。
