Combined statistical analysis of vasodilation and flow curves in brachial ultrasonography: Technique and its connection to cardiovascular risk factors

摘要

Clinical studies report that impaired endothelial function is associated with Cardio-Vascular Diseases (CVD) and theirrisk factors. One commonly used mean for assessing endothelial function is Flow-Mediated Dilation (FMD). Classically,FMD is quantified using local indexes e.g. maximum peak dilation. Although such parameters have been successfullylinked to CVD risk factors and other clinical variables, this description does not consider all the information contained inthe complete vasodilation curve. Moreover, the relation between flow impulse and the vessel vasodilation response tothis stimulus, although not clearly known, seems to be important and is not taken into account in the majority of studies.In this paper we propose a novel global parameterization for the vasodilation and the flow curves of a FMD test. Thisparameterization uses Principal Component Analysis (PCA) to describe independently and jointly the variability of flowand FMD curves. These curves are obtained using computerized techniques (based on edge detection and imageregistration, respectively) to analyze the ultrasound image sequences. The global description obtained through PCAyields a detailed characterization of the morphology of such curves allowing the extraction of intuitive quantitativeinformation of the vasodilation process and its interplay with flow changes. This parameterization is consistent withtraditional measurements and, in a database of 177 subjects, seems to correlate more strongly (and with more clinicalparameters) than classical measures to CVD risk factors and clinical parameters such as LDL- and HDL-Cholesterol.Keywords: Flow-Mediated Dilation, Cardio-Vascular Disease risks factors, Principal Component Analysis, endothelialfunction, image registration, diagnostic techniques.