Craiem Damian, Chironi Gilles, Simon Alain, Levenson Jaime
Universidad Favaloro, Facultad de Ciencias Exactas y Naturales, Buenos Aires, Argentina.
Am J Ther. 2008 Jul-Aug;15(4):340-4. doi: 10.1097/MJT.0b013e318164c6f0.
The vascular endothelium plays an important role in the regulation of vascular tone, cell growth, inflammation, and thrombogenicity. Endothelium dysfunction, then, is considered to promote several disorders that initiate the atherosclerosis process. Vascular tone dysfunction can be determined by high-resolution ultrasonographic imaging of the brachial artery, enabling one to assess endothelium-dependent flow-mediated dilation (FMD). It is based on the principle that an increase in blood flow, specifically in shear stress, provokes the release of nitric oxide and then a vasodilation that can be quantified. In this study, brachial artery diameter evolution was continuously followed during baseline and hyperemia after forearm occlusion using a custom designed software. Some techniques used to measure FMD are limited by operator dependence. We present a new, automated, and versatile method of FMD quantification based on B-mode echographic images and edge detection algorithms. Edges for each image in the acquired sequences are recognized as interfaces based on the grey-level profiles of the averaged pixel values. Within-reading and within-subject FMD% coefficients of variation were 7% and 10%, respectively. This technique largely improves manual measurements and was shown to be appropriate for wide clinical use.
血管内皮在血管张力调节、细胞生长、炎症及血栓形成过程中发挥着重要作用。因此，内皮功能障碍被认为会促使引发动脉粥样硬化进程的多种病症发生。血管张力功能障碍可通过肱动脉的高分辨率超声成像来确定，从而能够评估内皮依赖性血流介导的血管舒张功能（FMD）。其原理是血流增加，特别是切应力增加，会促使一氧化氮释放，进而引发可量化的血管舒张。在本研究中，使用定制软件在前臂阻断后的基线期和充血期持续跟踪肱动脉直径变化。一些用于测量FMD的技术受操作者依赖性限制。我们基于B型超声图像和边缘检测算法提出了一种新的、自动化且通用的FMD量化方法。根据平均像素值的灰度分布，将采集序列中各图像的边缘识别为界面。读数内和受试者内FMD%变异系数分别为7%和10%。该技术极大地改进了手动测量方法，且被证明适用于广泛的临床应用。
