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| Supercomputer copies whole-body blood flow | Supercomputer copies whole-body blood flow |
| (about 1 hour later) | |
| A new supercomputer simulation of blood moving around the entire human body compares extremely well with real-world flow measurements, researchers say. | A new supercomputer simulation of blood moving around the entire human body compares extremely well with real-world flow measurements, researchers say. |
| The software uses a 3D representation of every artery that is 1mm across or wider, scanned from a single person. | The software uses a 3D representation of every artery that is 1mm across or wider, scanned from a single person. |
| Its accuracy passed a first key test when physicists compared blood flow in the virtual aorta with the that of real fluid in a 3D-printed replica. | Its accuracy passed a first key test when physicists compared blood flow in the virtual aorta with the that of real fluid in a 3D-printed replica. |
| Flow patterns seen in the physical copy were a good match for the simulation. | Flow patterns seen in the physical copy were a good match for the simulation. |
| This was the case even when the fluid passing through the plastic aorta - and the virtual blood passing through the simulated aorta - was moving in pulses, to simulate the way blood is pumped by the heart. | This was the case even when the fluid passing through the plastic aorta - and the virtual blood passing through the simulated aorta - was moving in pulses, to simulate the way blood is pumped by the heart. |
| "We're getting extremely close results both in the steady flow and the pulsatile, which is very exciting," lead researcher Amanda Randles, from Duke University in Durham, North Carolina, told BBC News. | "We're getting extremely close results both in the steady flow and the pulsatile, which is very exciting," lead researcher Amanda Randles, from Duke University in Durham, North Carolina, told BBC News. |
| She presented the findings - including the comparison with a 3D-printed aorta - this week at the American Physical Society's March Meeting in Baltimore. The whole-body simulation itself was first unveiled at a computer science conference in November. | She presented the findings - including the comparison with a 3D-printed aorta - this week at the American Physical Society's March Meeting in Baltimore. The whole-body simulation itself was first unveiled at a computer science conference in November. |
| It is called "Harvey" - a tribute to the 17th-century physician William Harvey who first discovered that blood is pumped in a loop around the body. At the core of Harvey's computer code is a 3D framework, built up from full-body CT and MRI scans of a single patient. | It is called "Harvey" - a tribute to the 17th-century physician William Harvey who first discovered that blood is pumped in a loop around the body. At the core of Harvey's computer code is a 3D framework, built up from full-body CT and MRI scans of a single patient. |
| "It's not a common practice," said Dr Randles of the full-body scan. "But if we have it, then we can extract the arterial network. | "It's not a common practice," said Dr Randles of the full-body scan. "But if we have it, then we can extract the arterial network. |
| "We get a surface mesh representing the vessel geometry, then we decide what's a fluid node and what's a wall node, and then model fluid flow through there." | "We get a surface mesh representing the vessel geometry, then we decide what's a fluid node and what's a wall node, and then model fluid flow through there." |
| That modelling takes place on a supercomputer at the Lawrence Livermore National Laboratory in California. | That modelling takes place on a supercomputer at the Lawrence Livermore National Laboratory in California. |
| "It has 1.6 million processors, so it's one of the top 10 supercomputers," said Dr Randles, who worked in supercomputing at IBM before doing a physics PhD at Harvard, where she started work on Harvey. | "It has 1.6 million processors, so it's one of the top 10 supercomputers," said Dr Randles, who worked in supercomputing at IBM before doing a physics PhD at Harvard, where she started work on Harvey. |
| "The first stage was simply a proof of concept: can we actually model at this scale?" Most other simulations, she explained, have focussed on smaller sections of the circulatory system. | "The first stage was simply a proof of concept: can we actually model at this scale?" Most other simulations, she explained, have focussed on smaller sections of the circulatory system. |
| "The largest, I think, before this, was maybe the aortal-femoral region - so, the aorta down to about the knees." | "The largest, I think, before this, was maybe the aortal-femoral region - so, the aorta down to about the knees." |
| Modelling the flow inside every artery bigger than 1mm, at a resolution of 9 microns (0.009mm), a big step up. | |
| One of the project's aims is to test how different interventions in cardiovascular disease - such as stents or other surgical modifications - might affect the system more widely. | One of the project's aims is to test how different interventions in cardiovascular disease - such as stents or other surgical modifications - might affect the system more widely. |
| "We'll be able to change the mesh file, representing the vasculature, to represent different treatment options," Dr Randles said. | "We'll be able to change the mesh file, representing the vasculature, to represent different treatment options," Dr Randles said. |
| "Typically you would look at the local haemodynamic changes, but by having a simulation of the whole body we can see how that would affect the large-scale haemodynamics." | "Typically you would look at the local haemodynamic changes, but by having a simulation of the whole body we can see how that would affect the large-scale haemodynamics." |
| To validate Harvey's virtual blood flow against some real-world measurements, she added, the aorta - the biggest artery of them all - was an obvious choice. | To validate Harvey's virtual blood flow against some real-world measurements, she added, the aorta - the biggest artery of them all - was an obvious choice. |
| "You can end up having turbulent flow, which you're not going to see in other parts of the body. | "You can end up having turbulent flow, which you're not going to see in other parts of the body. |
| "We figured if we can do it there, then we've a good chance - we'd believe the rest of the model." | "We figured if we can do it there, then we've a good chance - we'd believe the rest of the model." |
| So her team collaborated with that of David Frakes, an engineer at Arizona State University, on a physical comparison. They used 3D printing to create a plastic version of the scanned aorta, so that fluid could be pumped through it and its flow tracked using shiny particles. | So her team collaborated with that of David Frakes, an engineer at Arizona State University, on a physical comparison. They used 3D printing to create a plastic version of the scanned aorta, so that fluid could be pumped through it and its flow tracked using shiny particles. |
| Seeing a faithful reproduction of what the simulation had come up with, Dr Randles said, was "pretty rewarding". | Seeing a faithful reproduction of what the simulation had come up with, Dr Randles said, was "pretty rewarding". |
| "It's pretty straightforward to calculate analytical solutions for flow in a pipe, or flow in a curved tube. But to make sure we're really getting an accurate simulation in a complex geometry was much more difficult." | "It's pretty straightforward to calculate analytical solutions for flow in a pipe, or flow in a curved tube. But to make sure we're really getting an accurate simulation in a complex geometry was much more difficult." |
| Next, she and her colleagues are turning their attention to the other half of the system; they are already building a mesh model of the same patient's veins. | Next, she and her colleagues are turning their attention to the other half of the system; they are already building a mesh model of the same patient's veins. |
| Ultimately, they hope to link the whole thing together with capillaries - the tiny vessels where red blood cells release their oxygen in single file - and even to move from fluid modelling to predicting the movement of all the individual blood cells. | Ultimately, they hope to link the whole thing together with capillaries - the tiny vessels where red blood cells release their oxygen in single file - and even to move from fluid modelling to predicting the movement of all the individual blood cells. |
| If that can be done, then simulating the progress of single cancer cells through the bloodstream will also be a possibility. | If that can be done, then simulating the progress of single cancer cells through the bloodstream will also be a possibility. |
| But that will require a future generation of supercomputers, Dr Randles said, with at least a thousand-fold more power. | But that will require a future generation of supercomputers, Dr Randles said, with at least a thousand-fold more power. |
| Her other hope is that their current high-level modelling will reveal the most important parameters to be measured and studied - so that patient-specific assessments can be done without the need for a supercomputer at all. | Her other hope is that their current high-level modelling will reveal the most important parameters to be measured and studied - so that patient-specific assessments can be done without the need for a supercomputer at all. |
| "We're trying to figure out what parts of the model we need to include, when," she explained. | "We're trying to figure out what parts of the model we need to include, when," she explained. |
| "The goal then would be to pare down the model and run it on something much more tractable." | "The goal then would be to pare down the model and run it on something much more tractable." |
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