Zoom down to one artery in your body, and the commotion is constant: blood cells hurtle down the passage with hundreds of their kin, bumping against other cells and the walls as they go. The many variables-and the sheer immensity of the human circulatory system-have kept scientists from closely documenting the rough-and-tumble life inside blood vessels.
Though we've come a long way from the ancient Greeks, who believed blood came from the liver, there's a surprising amount that we don't know about blood - particularly with regards to blood flow. This is an area of science called "biophysics," for the forces that govern red blood cells' movements at this level are best described by the laws of physics and can be mapped with mathematics.
Today, newer, faster HPC systems have allowed scientists to create detailed models of blood flow that help doctors understand what happens at the molecular level and, consequently, how heart and blood diseases can be treated. Now, a team of scientists from Brown University led by George Karniadakis are hoping that creating a better map will lead to better diagnoses and treatments for patients with blood flow complications.
Karniadakis' team needed access to huge amounts of computational power - and the expertise to use it - in order to create their model. They gained both by partnering with experts such as Joe Insley, a developer at the Argonne Leadership Computing Facility. Insley and his colleagues helped the Brown University team to parallelize and optimized their code for use on the Blue Gene/P HPC system, where they were allotted 50 million processor-hours.
"Previous computer models haven't been able to accurately account for, say, the motion of the blood cells bending or buckling as they ricochet off the walls," Insley said. "This simulation is powerful enough to incorporate that extra level of detail."
One part of the study is mapping exactly how red blood cells move through the brain. For example, last year the team used similar modeling to discover that the malaria parasite makes its victims' red blood cells 50 times stiffer than normal.
Healthy red blood cells are smooth and elastic; they need to squeeze and bend through tiny capillaries to deliver blood to all areas of the brain. But malaria-infected cells stiffen and stick to the walls, creating blockages in arteries and vessels. Malaria victims die because their brain tissues are deprived of oxygen. A more complete picture of how blood moves through the brain would allow doctors to understand the progression of diseases that affect blood flow, like malaria, diabetes and HIV.
Another part of the study seeks to understand the relationship between cerebrospinal fluid and blood flow in the brain.
"Blood vessels expand if blood pressure is high; and since they are located between brain tissues, this can put dangerous pressure on the brain," said Leopold Grinberg, a Brown University scientist on the team. In healthy people, spinal fluid can drain to relieve pressure on brain tissues, but occasionally the system breaks down-leaving the brain vulnerable to damage.
Said Grinberg, "Understanding how the system interacts will allow us to more accurately treat the problem."
To see a visualization of their preliminary results, please watch the embedded video. A version of this article first appeared on Argonne's website.
