Professor Suncica Canic Croatian-American mathematician uses math to build better stents

University of Houston mathematician Sunica Canic and her colleagues build computer models to study stents; their simulations could lead to better designs and also help doctors select the right stents for specific procedures

“I realized we could provide them with a fluid dynamics and mechanics point of view to help them make decisions…for example, about which stent grafts they use in their procedures,” she said.
Stents are tiny mesh tubes made from metal alloys that hold blood vessels open after they’ve been clogged with disease-causing plaque. Even though stents are designed to be compatible with the human body, they sometimes cause unwanted reactions, such as blood clots and scar tissue formation. So scientists have tried to coat stents with cells that make the tiny tubes even more compatible.
But these, too, aren’t yet perfect, said Canic. Blood flowing over a coated stent can still clot or tear cells away. This is, as Canic put it, “not good.” A professor of mathematics at the University of Houston, Canic makes computer models to guide the search for a better stent coating.

She also uses computer models to study the strengths and weaknesses of different stent structures. Her work could help manufacturers optimize stent design and help doctors choose the right stents for their patients, ultimately improving patient outcomes.
Computer scientists usually model stents in three dimensions. Keeping track of about 200,000 points, or nodes, along the stent mesh, the models are massive.
Together with her collaborator Josip Tambaca of the University of Zagreb in Croatia, and her Ph. D. student Mate Kosor, Canic wrote a much simpler program that approximates stents as meshes of one-dimensional rods. This program let them achieve the same result using just 400 nodes.

Using their simplified model, the researchers have examined the designs of several stents on the market to see which structures seem to be best for specific blood vessels or procedures. For instance, they found that stents with an “open design” — where every other horizontal rod is taken out — bend easily, which makes them good to put in curvy coronary arteries.
Canic has also used the model to design a stent with mechanical properties specifically tailored to an experimental heart-valve replacement procedure. She found that this specialized stent works best for the procedure when it’s stiff in the middle and less stiff at the ends. In addition, she has found that combining bendiness with radial stiffness — where you can bend the stent into a U shape, but you can’t squeeze the tube shut — produces a stent with less chance of buckling than those that are currently in use.
The most rewarding part of her work, said Canic, is that “we can use mathematics for something useful, connected to real-world problems.” She reports that her collaborators are already putting the results of her simulations into practice.
Meanwhile, her greatest challenge is serving as an ambassador of mathematics to the medical and bioengineering communities.

In the beginning, she said, it was difficult to collaborate with people from different disciplines who speak different scientific languages. “But once they saw that there is a lot of information there that could be helpful, it has been much easier,” she said. “Now people want to talk to us from the medical center. They come to us and ask questions, and that’s good.”
Today, Canic is collaborating with Prof. Boris Muha (University of Zagreb),  Prof. Martina Bukac (University of Pittsburgh), Prof. Annalisa Quaini (University of Houston), and Dr. Stephen Little (Methodist Hospital in Houston) on modeling a novel experimental procedure for heart valve replacement, called Transcatheter Aortic Valve Replacement (TAVR).
Since only a few years ago, patients with failing aortic valves no longer need to have open-heart surgery. All that is needed is a small cut in the patient’s  groin area, where a catheter, holding a bioartificial valve, is placed and guided through the patient’s arteries, all the way to the location of the failing aortic valve. The valve, which is mounted on a stent, is then pushed out of the catheter, and a self-expanding stent anchors the valve in the location of the failing valve.
Modeling the function of the new valve, and of the stent holding the valve, is what Canic and her team are investigating these days. In their medical collaborator’s lab, 3D printing of human organs, and parts of the patient’s cardiovascular system surrounding the aortic valve, combined with mathematical modeling and computer simulations, are being used for patient-specific simulations of this procedure. “What was science fiction yesterday, is reality today,” says Canic.
Source www.livescience.com