Author Topic: Clinical and Computational Study of Geometry& Heamodynamics of Arterial Stenosis  (Read 2843 times)

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Author : Krittika Dasgupta, Abhirup Roy Choudhury, Abhijit Chanda, Debabrata Nag
International Journal of Scientific & Engineering Research, IJSER - Volume 2, Issue 4, April-2011
ISSN 2229-5518

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Abstract— Stenosis is abnormal narrowing of blood vessels. The presence of stenosis in arteries may cause critical flow conditions. It may finally lead to stroke and heart-attack. A clinical study has been done on more than 130 patients along with computational study using 2D axisymmetric rigid model of stenosis in the carotid artery. Assumed shapes of deposition zone and the degree of occlusion used in the analysis were taken from clinical data. The Navier-Stokes equations for incompressible fluid flow have been considered as the governing equations and it has been solved with varying flow parameters using standard CFD software package. The radial velocity profiles at various points of the flow field, the centerline velocity plot and the centerline pressure plots have been obtained from computational study and compared with the clinical data.

Index Terms— Arterial flow, Clinical validation, Computational Fluid Dynamics, Heamodynamics, Mathemetical Modeling, Stenosis, Stenosis geometry.

INTRODUCTION                                                                     
IN the present century arterial stenosis is one of the  major causes behind death in all parts of the globe.  Arterial Stenosis is abnormal narrowing or restriction present in the inner wall of blood vessel due to the depo-sition of cholesterol, fatty materials, cellular waste etc. It may happen in all large or small arteries, commonly in Coronary artery, Carotid artery, and Peripheral artery. In the present case study we only emphasize on Carotid  artery stenosis. Carotid artery is one of the larger arteries, present in our neck region. The normal geometry of the artery is divided into three segments, Common Carotid Artery (CCA), External Carotid Artery (ECA) & Internal Carotid Artery (ICA). The deposition of plaque may vary in shape: simple to complex structures and in dimension. Flow through these complex structures is commonly   associated with flow separation, stagnation, recirculation, secondary vortex motion, plaque rupture etc.
Efforts have been made to model stenosis and its complex hemodynamics by Computational Fluid Dynamics (CFD) and experimental analyses since 1990’s. Ku and others have made detailed studies on the fluid mechanics of vascular systems hemodynamic changes due to stenoses [1, 2]. Johnston and Kilpatrick (1991) studied the effect of geometrical irregularities in the wall of a stenosed artery for Reynolds numbers from 20 to 1000 [3]. Tang et al [1995-1998] used 3D models for steady viscous flow in an elastic stenotic tube with various stenosis stiffness and pressure conditions [4]. In past experiments blood flow has been considered both as Newtonian or Non-Newtonian fluid depending upon the radius of the blood vessel. Haemodynamic studies have been made for both steady and pulsatile flows. However, no special emphasis is given in the stenosis geometry and previous studies used idealized models using definite curves (Cosine curve, Smooth curves, Irregular Geometry). In this study, a detail care has been taken to obtain more realistic stenosis geometry after going through more than 130 patient’s real time Ultrasound Doppler Examination data.

2   CLINICAL STUDY
2.1 Data Collection
More than 130 ultrasound images of vascular stenosis have been acquired for our analysis of Carotid arterial stenosis. All these patient data have been collected ran-domly from different well-known multi specialty hospit-als in eastern India. It has been ensured during data col-lection and throughout the work that no patient identity is revealed. Only the information about age and sex has been noted along with other necessary clinical informa-tion for every patient data.

2.2 Study and Analysis
Each patient data are reviewed thoroughly and very carefully to identify the common geometry and occurrence of stenosis/plaque in the artery. Maximum and minimum deposition heights, length of constriction, percentage of diametric reduction are also noted for each and every data.

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