The geology of the human heart
26 March 2009
Geologists investigating how planets form have found an unlikely application for their research: modelling blood flow in diseased hearts.
Blood flow in an artery. Research to model molten metal flow in meteors has helped doctors locate blood clots in hearts.
The finding has already helped surgeons confirm the location of a potentially life-threatening blood clot in a patient at the Royal Bournemouth Hospital.
Scientists are known for their ability to think laterally. But a researcher at Bournemouth University has taken this further than most. Professor Nick Petford, a geologist and Pro Vice-Chancellor at the university had been investigating the early formation of planets.
At the centre of a planet like Earth lies a solid inner core. It is believed to be made up mainly of iron with some nickel. Surrounding the inner core flows a liquid metal outer core 2200 kilometres beneath the surface.
An artist's impression of planetary formation.
'The question has always been: how did the core form?' says Petford, whose work is funded by the Natural Environment Research Council.
The theory is that terrestrial planets started out as small chunks of rock that merged together. But scientists lacked vital information about how liquid metal made it into the centre of the growing planets.
'For a long time people thought the flow of liquid iron along the edge of grains and through narrow channels and cracks was not possible,' says Petford.
Researchers know about how planets form by examining meteorites, which are relics of planetary formation.
'We solved the fluid flow equations around the meteorite straight from the images. But the trick is, it could be any image.'
Petford's colleague, Professor Tracy Rushmer at Macquarie University, Sydney, experimented on real meteorites to see what would happen when they were deformed by intense heat and pressure. They wanted to see how the molten iron moved in millimetre-wide fissures. The experiments were successful and Petford worked out how molten metal streamed through these channels.
'Once you establish how metal flows in cracks then you can develop computer simulations to see how fast it moves.'
Mental leap
The big jump came when Petford realised the same idea could be applied to other areas of science and even medicine.
A drawing of the human heart. Subtle differences in shape affect blood flow. Click to enlarge.
He had taken detailed photographs of meteorites and their cracks and fissures. 'We solved the fluid flow equations around the meteorite straight from the images. But the trick is, it could be any image, not necessarily a meteorite,' explains Petford.
He teamed up with a heart specialist at the Royal Bournemouth Hospital. They experimented with some MRI scans of carotid arteries which pump blood from heart to the brain - you can feel these arteries pulsating just under your jaw on either side of your neck.
The scientists imported the geometry of the arteries into their newly-developed software and used the same methods as before to model the flow. But instead of modelling liquid metal at temperatures hovering around 1000ºC, they were now simulating blood flow.
'If you have an image and you know fluid flows in it, we can solve the fluid flow equations for that specific geometry,' says Petford.
The key parameters the researchers needed to change were the viscosity and density of the fluid.
The breakthrough for medicine could be profound. We are all familiar with medical diagrams of the layout of veins and arteries in a body. But these are idealised representations: everyone is unique.
'All vascular systems are different,' explains Petford. 'What we can start to think about now are bespoke blood flow models.'
The first application could be in heart surgery. Blood flow around and through a heart depends on its shape: every heart is subtly different and has a unique blood flow signature.
The scientists have used the new technology to analyse blood flow in the heart of a patient at the hospital. The surgeons knew that probably somewhere in the patient's diseased heart there would be an area of stagnant blood which could cause a blood clot.
The location of the stagnant flow was not obvious from the MRI scan. But when the researchers used the software to analyse the scan they predicted the clot's location correctly.
The blood flow simulations and subsequent diagnosis takes several hours to several days. 'We have shown the principle works across disciplines. The next step is to develop its medical applications,' added Petford.
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