Geometry optimization of arterial grafts: steady flow

Abstract

Bypass surgery might require grafts to re-establish blood flow in severely stenosed or fully occluded arteries. The bypass configuration, including the geometry of graft and the anastomosis, has a strong influence on the blood flow dynamics, inducing recirculation flows and formation of stagnation zones, directly related with after-surgical restenosis. Optimization techniques coupled with numerical simulation codes can and must be used to find solutions that guarantee the minimization of after-surgical risks. Search for optimized graft geometries has been presented in the literature, most of the times, restricted only to one objective function. New research for the development of a new methodology for multi-objective optimization of grafts is presented here. In contrast to optimization methodologies of one objective function, the solutions to this problem are not a single point but a family of points, allowing a selection in accordance with the experience of the investigator in vascular surgery. The methodology of this research on multi-objective optimization considers a genetic algorithm searching optimal sinusoidal bypasses geometries iterating over simulation results obtained with a finite element method application developed for the simulation of blood flow. As objective functions it is addressed the optimization of the flow efficiency, minimizing the pressure variation and simultaneously minimizing of zones of occurrence of blood stagnation and recirculation flows. Obtained numerical results exhibit the benefits of arterial graft geometry optimization prior to bypass surgery, minimizing recirculation and stagnation zones and diminishing the after-surgical probability of arterial restenosis. This work represents the formal use of multi-objective algorithms in the optimization design of hospital vascular surgery.