Optimization Study of the Hemodynamics of Saline Flushing in Endoscopic Imaging of Chronic Total Occlusions (CTOs).

In this study, in vitro experiments and computational fluid dynamic (CFD) simulations are used to expand the understand of the physics of saline flushing of a blocked artery to enable optical imaging. This process involves saline injection, mixing with blood, and advection of the mixture away from the region of interest to provide a clear optical path for imaging. CFD simulations are used as a rapid turn-around tool for the evolutionary design process of an endovascular catheter that combines imaging forward-viewing element with saline flushing lumens. A novel design and control technique is developed that provides the method to regulate the pressure in a blocked artery during saline flushing, so only small deviations from physiological pressure values are exerted on the damaged artery wall at any time, minimizing risk of rupture. In vitro experiments demonstrate the optical clearing process in phantoms simulating chronic total occlusions (CTOs) in coronary arteries with an opaque blood surrogate being removed by saline flushing. With the CFD compared by the experiments, parametric analyses of artery diameter and curvature, and flushing lumen diameter size were conducted to understand their impact on flushing times and pressures. Different plaque morphologies were studied to explore the feasibility of saline flushing in different CTO conditions. A new catheter design is demonstrated to safely and effectively produce saline flushing, leading to a clear optical imaging field, and an improved technique is outlined that overcomes some practical challenges and limitations commonly encountered in angioscopy.