Blood flow modeling through stents ignites passion for biomedical engineering

An interest in solving complex problems, friends training to be medical doctors and his father having a stroke helped put John Asiruwa on the path to becoming a biomedical engineer.

That journey began in Benin City, Nigeria, when Asiruwa earned his bachelor's degree in mechanical engineering from the University of Benin. After working as a process engineer for a year, he decided to pursue a master's degree. His uncle Christopher Igbinedion, who earned his master's degree in civil engineering in 1993 from South Dakota State University, recommended his alma mater.

Then Asiruwa did his homework—his search led to associate professor Stephen Gent, who is modeling blood flow through stent grafts. "I had a basic knowledge of pipe flow because I had been a process engineer, so why not apply these principles to the human body?" Asiruwa thought. When he arrived at SDSU in fall 2015, his first stop was Gent's office.

"I want to learn," Asiruwa recalled telling Gent. "I want to be able to think outside the box, to be involved in something that can make life better for others."

Learning the Ropes
Asiruwa began by taking a new special topics course, Engineering Mechanics in Biomedical Applications in fall 2015, which Gent developed as an extension of his biomedical research and as part of the biomedical engineering minor. "I was scared," Asiruwa admitted. "It was my first graduate class in a different country, but it was new to everyone."

When Gent talked about his research with Sanford Health modeling blood flow through stents, Asiruwa was hooked. Gent described aneurysms and how stent grafts could improve outcomes for patients, he recalled. 'I knew a brain aneurysm rupture was the cause of my father's stroke in 2012."

Gent has been collaborating with Sanford Health vascular surgeon Dr. Pat Kelly and biomedical engineer Tyler Remund, who is part of Kelly's product development team, to evaluate blood flow through stent grafts since 2014. The results of their work have been published in the Journal of Vascular Surgery. The data from Gent's computational fluid dynamics simulations support Sanford Health's efforts to commercialize these life-saving devices.

Asiruwa began his graduate work as a teaching assistant, grading homework assignments, first, for a fluid mechanics class and then thermodynamics. "That helped me refresh my memory," explained Asiruwa. In spring 2016, he took two more graduate classes, one in computational fluid dynamics and another in advanced fluid mechanics.

In addition, he met weekly with Gent to discuss papers on blood flow modeling and stent graft designs .As Asiruwa began learning the computational fluid dynamics software, he became what he called "the post-processing guy" for the stent graft modeling team, eventually transitioning to a research assistantship.

Gent said, "I have been quite impressed with John's enthusiasm and abilities. He has proven to be an asset for our research group."

Modeling coronary arteries
Working with Gent and students modeling stent grafts for the summer National Science Foundation Research Experience for Undergraduates program gave Asiruwa an idea for his own research.

"A stent is difficult to deploy in a coronary artery," he explained, noting the critical role that blood pressure and flow dynamics play in this part of the body.

Asiruwa is using CFD modeling to evaluate how the angle at which the coronary artery branches affects the blood flow and, therefore, the likelihood of clotting and plaque buildup known as atherosclerosis. This information is vital when carrying out coronary bypass surgeries and placing stents.

"The takeoff angle of the left coronary artery makes a difference," he pointed out. Based on these analyses, he hopes to identify which angles are associated with an increased likelihood of blockages reoccurring. The results will give surgeons data to make decisions that will affect patient outcomes.

"Understanding the flow dynamics in coronary stenting and its complexity will help those designing biostents and tissue-engineered degradable stent grafts for more complex aneurysm-prone regions with delicate arterial networks," explained Asiruwa. He hopes one day to do research on stents used for brain aneurysms.

Asiruwa credits Gent and his work with Sanford for igniting his passion for biomedical engineering. Once he completes his master's degree, he wants to pursue a doctorate in biomedical engineering at the University of South Dakota and continue doing research on Sanford Health projects.

"I come from an area of the world where minimally invasive medical techniques are not common," he explained. Through working on this research, Asiruwa said, "I feel I am in the right place. I can see what I am doing can be life changing for patients."