Numerical and experimental investigations of blood flow with application to vascular bypass surgeries.

摘要

In planning operations for patients with cardiovascular disease, vascular surgeons rely on their training, past experiences with patients with similar conditions, and diagnostic imaging data. However, variability in patient anatomy and physiology makes it difficult to quantitatively predict the surgical outcome for a specific patient a priori. A simulation-based medical planning system that utilizes three-dimensional finite element analysis (3D FEA) methods and patient-specific anatomic and physiologic information to predict changes in blood flow distribution and flow patterns resulting from surgical bypass procedures has been developed. However, in order to apply these computational methods, their accuracy must first be determined.; In this dissertation, velocity and flow measurements acquired with phase contrast magnetic resonance imaging (PC-MRI) techniques were compared against those predicted using the 3D FEA methods for a bypass geometry. Studies were performed both in a phantom model of a stenosed vessel with a bypass graft and in pigs that had undergone thoraco-thoraco aortic bypass graft procedures.; The phantom experiments consisted of comparisons of flow rates and flow patterns at five distinct locations in the model and under both a lower and higher Reynolds number, thus examining a range of flow complexities not investigated by previous studies. These experiments highlighted the differences between PC-MRI and the 3D FEA methods and resulted in the development of post-processing steps critical for the fair comparison of results from the two techniques. They were also used to examine the sensitivity of the 3D FEA results to various input parameters, such as the geometric model.; The methods developed for the phantom experiments were applied to comparisons between the 3D FEA results and the PC-MRI data for the more challenging in vivo experiments. Flow distributions and flow patterns were modeled and compared against PC-MRI measurements acquired at two locations in the porcine studies. These comparisons are the first in vivo investigations of these simulation methods for bypass surgery planning purposes and as such, they represent an important step towards this new paradigm in medicine.