2017; 02(05): 085-095 men/17/1721/gmj

Original Research Article

Hemodynamic Abnormalities in a Carotid Bifurcation Based on Doppler Ultrasound Imaging

Catarina F. Castro1,*, Luisa C. Sousa1, Helena A. M. Henriques2, Carlos C. António1, Rosa Santos3, Pedro Castro3 and Elsa Azevedo3
11INEGI and DEMec, Faculdade de Engenharia da Universidade do Porto, Porto, Portugal
2INEGI, Institute of Science and Innovation in Mechanical and Industrial Engineering, Campus da FEUP, Porto, Portugal
3Departmento de Neurologia, Hospital de S. João e Faculdade de Medicina da Universidade do Porto, Porto, Portugal

Correspondence to
Catarina F. Castro, INEGI and DEMec, Faculdade de Engenharia da Universidade do Porto, Porto, Portugal

First Published Online 29 june 2017

ABSTRACT

Carotid Doppler ultrasound and imaging, are focused on the visualization and measurement of blood flow, providing critical diagnostic information noninvasively about fluid dynamics and abnormalities. Ultrasound imaging is a complicated interplay between physical principles and signal processing methods. In this work, the development of a new algorithm for lumen identification and segmentation in ultrasound images is reported. In longitudinal images, a fully automatic technique based on row-wise pixel intensity distribution alleviates the laborious and time-consuming manual evaluation of the lumen. Then a region growing methodology is applied ensuring convergence from lumen identification to lumen boundary. However, for carotid transversal images, a semi-automatic methodology must be adopted due to image specification. Computational fluid dynamics is a powerful tool to investigate the hemodynamic behavior in the carotid bifurcation. A patient-specific analysis is presented. Carotid artery bifurcation reconstructions based on a combining set of longitudinal and transversal ultrasound images were considered as input geometry for three-dimensional computational fluid dynamics. Inlet pulsatile velocity obtained from Doppler ultrasound measurements is considered. Computation based on assumptions such as incompressible and Newtonian fluid, rigid vascular wall and non-slip condition at wall suggests a complicated hemodynamic behavior. Vessel wall shear stress parameters were derived from the simulated velocities on the complex three-dimensional geometry revealing hemodynamic abnormalities consistent with sites of local development and progression of atherosclerotic disease.

Keywords: algorithms, ultrasound image segmentation, surface reconstruction, computational fluid dynamics, wall shear stress parameters

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