Asymmetric pulsation of rat carotid artery bifurcation in three-dimension observed by ultrasound imaging

Abstract The arterial structure cyclically fluctuates in three-dimensions (3-D) caused by pulsatile blood flow. The evaluation of arterial wall motion and hemodynam- ics contributes to early diagnosis of carotid atherosclerosis. Ultrasound is one of the most appropriate imaging modali- ties to evaluate arterial wall motion in real time. Although many previous studies have discussed the mechanical properties of the carotid artery bifurcation (CAB) from the two-dimensional (2-D) view, the spatio-temporal variation of carotid artery geometry in 3-D has not yet been investi- gated in detail. In this study, the 3-D data set of CAB from rats was acquired using a high spatio-temporal resolution ultrasound imaging system with a 40 MHz probe using mechanical sector scanning. A total of 31 slices of cross- section images were stored and a spoke scan algorithm was implemented to radially scan the lumen area in polar coor- dinates based on a pre-tracked seed point. The boundary of the arterial lumen was segmented using intensity-thresh- old-based boundary detection and fitted by polynomial regression. Two operators, who were trained with the same protocol to minimize inter- and intra-operator variability, manually segmented the lumen boundary on systolic and Electronic supplementary material The online version of this article (doi:10.1007/s10554-016-0934-9) contains supplementary material, which is available to authorized users. Dong-Guk Paeng paeng@jejunu.ac.kr 1 Department of Ocean System Engineering, Jeju National University, Jeju, South Korea 2 Interdisciplinary Postgraduate Program in Biomedical Engineering and Ocean System Engineering, Jeju National University, Jeju, South Korea diastolic phase from the gray-scale images. Finally, the 3-D lumen geometries of CAB during one cardiac cycle were constructed based on the segmented lumen boundar- ies. From this constructed 3-D geometry, we observed that the CAB geometry favorably expanded to the anterior/pos- terior direction, parallel to the sagittal plane; and the manu- ally segmented geometry also confirmed the asymmetrical change in bifurcation geometry. This is the first study on visualization and quantification on the asymmetrical varia- tion of the CAB geometry of a rat in 3-D during a whole cardiac cycle. This finding may be useful in understanding hemodynamic etiology of various cardiovascular diseases such as arterial stenosis and its complications, and also provides reference information for numerical simulation studies