CFD techniques apply advanced computer processing capabilities to perform millions of repetitive operations that mimic the flow of blood through the arteries and help to create an image of the process. One challenge faced by researchers using CFD is the tremendous volume of information produced – sometimes terabytes – which can overwhelm traditional visualization tools.
Fortunately, that's not an issue for Karla Vega, a graduate research assistant within the Texas Advanced Computing Center (TACC) Visualization and Data Analysis group, a research enterprise at The University of Texas at Austin. TACC provides advanced computing resources and services to enable computationally intensive research, and also collaborates with individual researchers to apply advanced computational techniques in their specific research activities.
Vega is working with Yuri Bazilevs, a post-doctoral Fellow with the Institute for Computational Engineering and Sciences, to develop precise, three-dimensional blood-flow velocity animations utilizing EnSight Gold simulation software from Computational Engineering International, Inc. These types of animations will likely play a crucial role one day in diagnosing and treating aneurysms in clinical settings.
EnSight Gold supports models that contain millions or billions of nodes, providing unmatched parallel processing and rendering for intensive applications such as blood flow animation. EnSight software is installed on several TACC computers and used regularly by the researchers there.
"Seeing the characteristics of the blood flow is crucial to the research we are doing, and EnSight allows you to perform animations very easily," explains Vega. "Blood flow is all about volume, and EnSight's volume rendering technique is superior to other visualization software. It's very interactive, as well, so it allows us to have more and different viewpoints than traditional software."
Sophistication of the rendering process is crucial to the precision required in medical research. Surfacing, streamlining and contouring are coupled with fluid structural simulations. Unlike solid external structures, such as a lead or steel pipe, arteries move with every beat of the heart, and the software must be able to plot these movements and the associated stress and pressure distribution to visualize exactly what is happening inside the blood vessel walls.
"One aspect of this that is very exciting is that we are performing these calculations on patient-specific geometries, so the animations that Karla develops correspond to a real person," explains Bazilevs. "These models are setting the groundwork for actual use one day in clinical settings to assist in identifying diseases of the cardiovascular system and in surgical treatments that may be required."
Vega's work is expanding beyond aneurysms. As more and different data sets become available, she is developing visualizations of other parts of the cardiovascular system and arterial walls.
"As I receive more data sets, I try to look at different aspects of the blood flow and the unique characteristics of different types of aneurysms, such as aortic and thoracic. For example, the velocity field in an abdominal aorta aneurysm is more unsteady compared to that in a cerebral aneurysm."
Vega and Bazilevs believe that the daily use of this technology in a clinical setting is still in the future, though the ultimate benefits are clear.
"This will definitely be used someday," says Bazilevs. "Today, the models are still quite complex and would be challenging for physicians to use in a clinical environment, but we are working with doctors to explain the value of this application and they are getting more and more excited by the possibilities this presents as part of the medical decision-making process."
EnSight software allows us as researchers to fully explore all aspects of the data and enables us to visualize and animate it as if a movie were playing," Vega says. "We can change views, select different attributes and change those attributes to our liking. We can certainly do a lot of different things, and the capabilities of EnSight makes it much easier."
As medical diagnostic technology continues to evolve and harness the capabilities of animation and visualization, researchers such as Vega and Bazilevs will look to advanced tools like EnSight Gold simulation software in order to process and analyze extremely large data sets and find specific features for specific visualizations.
In doing so, they are paving the way for new applications of computational flow dynamics and visualization/animation that are laying the groundwork for breakthroughs in future medical care.
Some 15,000 Americans die each year from ruptured aortic aneurysms alone, and it is the 10th leading cause of death in men over age 50 in the U.S. In the TACC lab in Texas, Vega is pleased to play a role in possibly reducing that number.
"The capabilities provided by this software allow me to feel that I making a personal contribution to something important," Vega says. "Even though I work with this technology every day, it is still personally rewarding to me to complete a simulation and know that it is laying the groundwork for something that may help enhance the quality of life for many people in the future."
Blood flow streamlines in an abdominal artery.