Computational analysis of the effectiveness of blood flushing with saline injection from an intravascular diagnostic catheter

Abstract

Optical techniques including fluorescence lifetime spectroscopy have demonstrated potential as a tool for study and diagnosis of arterial vessel pathologies. However, their application in the intravascular diagnostic procedures has been hampered by the presence of blood hemoglobin that affects the light delivery to and the collection from the vessel wall. We report a computational fluid dynamics model that allows for the optimization of blood flushing parameters in a manner that minimizes the amount of saline needed to clear the optical field of view and reduces any adverse effects caused by the external saline jet. A 3D turbulence (k - ω) model was employed for Eulerian-Eulerian two-phase flow to simulate the flow inside and around a side-viewing fiber-optic catheter. Current analysis demonstrates the effects of various parameters including infusion and blood flow rates, vessel diameters, and pulsatile nature of blood flow on the flow structure around the catheter tip. The results from this study can be utilized in determining the optimal flushing rate for given vessel diameter, blood flow rate, and maximum wall shear stress that the vessel wall can sustain and subsequently in optimizing the design parameters of optical-based intravascular catheters.

Keywords: Eulerian-Eulerian two-phase flow; k − ω turbulence model; mixture model; multiphase flow.

Figure 1

2D schematic view of the catheter: (a) top view and (b) side view (all dimensions are in mm) and (c) computational tetrahedral mesh at the midplane.

Figure 2

Grid independence study for case 1: (a) maximum saline concentration profile on the blood vessel, (b) maximum WSS on the blood vessel wall caused by saline injection, (c) maximum WSS on the blood vessel wall caused by blood, and (d) maximum pressure change profile on the blood vessel wall.

Figure 3

Grid independence study for case 3: (a) maximum saline concentration profile on the blood vessel, (b) maximum WSS on the blood vessel wall caused by saline injection, (c) maximum WSS on the blood vessel wall caused by blood, and (d) maximum pressure change profile on the blood vessel wall.

Figure 4

Comparison of results obtained using Eulerian–Eulerian and mixture models for case 1: (a) maximum pressure change profile on the blood vessel wall along the flow direction, (b) maximum saline concentration profile on the blood vessel wall, and (c) maximum WSS profile on the blood vessel.

Figure 5

Streamlines showing the flow structure on the midplane: (a) case 1, (b) case 2, (c) case 3, and (d) case 4 and saline phase concentration contour on the midplane: (e) case 1, (f) case 2, (g) case 3, and (h) case 4.

Figure 6

Saline phase concentration contour on the midplane: (a) case 1, (b) case 2, (c) case 3, and (d) case 4.

Figure 7

Comparison of results for four different cases: (a) distribution of the maximum WSS on the blood vessel along the flow direction, (b) maximum wall pressure profiles along the flow direction, and (c) distribution of maximum saline concentration on the blood vessel wall along the flow direction.

Figure 8

Comparison of results for 6-mm diameter vessel with uniform and pulsatile blood flow rates: (a) distribution of maximum WSS on the blood vessel wall, (b) distribution of maximum saline concentration on the blood vessel wall, and (c) maximum wall pressure change on the blood vessel wall along the flow direction.