Shadden Lab: Diagnosing cardiovascular disease via simulation
By Victor Zendejas Lopez and Richard Didham
Cardiovascular disease is the leading cause of premature death in the United States. Despite how common heart disease is, it is often difficult for medical practitioners to accurately determine an optimal treatment strategy due to the high complexity of the human body. One promising solution to this problem is currently being developed by mechanical engineering professor Shawn Shadden and The Shadden Lab at the University of California, Berkeley.
The Shadden Lab develops computational tools that model and simulate blood flow within the cardiovascular system. Shadden’s work, often termed as cardiovascular simulation, will give doctors new insights into the complex relationships between blood flow, blood pressure, and the overall function of the cardiovascular system. While the technology is still developing, it has the potential to revolutionize the way doctors diagnose and treat cardiovascular disease.
How Does Cardiovascular Simulation Help Doctors?
Cardiovascular simulation gives doctors critical information related to the functionality of a patient’s cardiovascular system, and what treatment strategy will work best for that patient. When a doctor looks at a MRI or CT scan of a patient, they don’t receive very much functional information regarding the complex fluid flow through that person’s heart or vessels. As a result, there is a lot of “guesswork” involved in treating patients with cardiovascular problems. Doctors will asses the situation with limited information and make a prediction about how the human body will react to various treatment strategies.
The problem with this approach is that it does not accurately capture the complexity of the human body and the diversity of the human population. Cardiovascular simulation addresses this issue by giving doctors significantly more patient specific information on what is happening in a patient’s body and in turn, allows doctors to create more effective treatment protocols.
How Does Shadden Simulate the Cardiovascular System?
Finite Element analysis is a tool used by scientists and engineers to model and simulate complex systems such as modeling drag over an airplane or predict how a building will behave during an earthquake. With advances in modern computing, tools such as finite element analysis have become more powerful and are now able to analyze more complicated systems-such as the human cardiovascular system.
Imagine the plumbing in your home. You have water flowing through a pipe at a steady rate, we can readily find direct relationships in this system such as the velocity of the fluid and pressure. The reason we can readily do this is because we have straight and constant geometry. Now imagine the cardiovascular system where the vessel walls are now longer rigid and there are drastic changes in vessel diameter from one section to the next. This renders the process of finding relationships between the fluid flow and pressures more difficult.
The simulations conducted by the Shadden Lab begin with a snapshot of a patient’s cardiovascular system via an MRI or CT scan. From this scan, researchers create a 3D image and a finite element model is built. From this model, conditions are specified throughout the region such as wall deformability how much blood is pumped into the system. From specifying these conditions we can determine relationships between blood pressure and blood flow at different regions within the cardiovascular system.
How Accurate is Cardiovascular Simulation?
While Shadden’s simulation research shows a lot of promise, there are a few hurdles that must be overcome before this research is ready to be applied in a clinical setting. Ultimately, these hurdles are due to a lack of data available to researchers simulating the human body. Since Shadden’s Lab can’t easily measure pressure or fluid velocity within the cardiovascular system, it is difficult to validate the pressure and fluid velocity that their simulations predict.
This problem with accuracy also creates another issue when it comes to tuning simulations for specific patients. There is an incredible amount of diversity within the human population when it comes to the human cardiovascular system. Depending on factors such as age, genetics and lifestyle, different people may have stiffer vessel walls, or may have higher blood flow rates than others even though their arteries could look exactly the same in a MRI scan. As a result, Shadden must make educated guesses about how to tune his simulation techniques to account for diverse body types.
Shadden remains optimistic about the data challenges that cardiovascular simulation currently faces. He believes this problem will be addressed naturally over time. As our fundamental understanding of the cardiovascular system improves, researchers will be able to conduct more accurate cardiovascular simulations; as a result, we gain an even better understanding of the cardiovascular system and can produce even more accurate cardiovascular simulations. This “positive feedback loop” will come about as more research is conducted in the field of cardiovascular simulation.
One way in which Shadden hopes to accelerate research in his field has been through the Simvascular Software project. Simvascular is an open source (free for anyone to download) cardiovascular simulation software package that integrates cardiovascular simulation techniques that Shadden and colleagues have developed to streamline the cardiovascular simulation workflow. The project was created to enable broader research in the field of cardiovascular simulation by the research community. Since its release in 2014 the project has been very successful, with more than 13,000 downloads of the software by simulation researchers all over the world.
Prof. Shadden stated the potential impact of his research work very succinctly by making an analogy between his work and the aerospace industry: Many years ago when people designed airplanes, they would build an airplane and find out if it flies. However, they do not do that anymore. Now, aerospace engineers run numerous simulations to build confidence that a design is going to provide the expected outcome. Shadden says his lab “aims to do something very similar, but now for human health care. Instead of asking what might work and then learning by trial and error on actual patients, can we virtually perform these treatments or these changes and see what will happen.”
The work engineers do shapes the world around us. But given the technical nature of that work, non-engineers may not always realize the impact and reach of engineering research. In E185: The Art of STEM Communication, students learn about and practice written and verbal communication skills that can bring the world of engineering to a broader audience. They spend the semester researching projects within the College of Engineering, interviewing professors and graduate students, and ultimately writing about and presenting that work for a general audience. This piece is one of the outcomes of the E185 course.