June 7, 2013 6:19 pm

New visions of the human heart

Groundbreaking scanning techniques reveal far more about our inner workings than traditional X-rays
Computer model of a human heart©Nic Smith, Matt Sinclair and Eoin Hyde

Imaging is transforming medical diagnostics, as newer scanning techniques reveal far more than traditional X-rays about what is going on inside our bodies.

The heart and its cardiovascular system are particularly important for medical imaging, given the amount of disease they cause. But they are hard targets: it is difficult to image objects in motion, such as a beating heart and pulsing arteries, and the diagnostic signs of an impending heart attack are small and subtle. Three new approaches to cardiac imaging are under development at the biomedical engineering and imaging centre in St Thomas’ Hospital, part of King’s College London.

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“The overall aim is to move from generalised diagnostics, based on studies of populations in which there is inevitably huge variability, to procedures that show what is happening to each individual patient,” says Reza Razavi, the cardiologist who heads the centre, just across the Thames from the Houses of Parliament.

One project is looking at atherosclerosis, the build-up of fatty plaques in the arteries. When a plaque breaks away a clot may form, blocking the blood flow and starving the heart of oxygen – causing a heart attack. When examining an individual, the cardiologist wants to know which, if any, of the fatty plaques is likely to rupture.

Microscopic cross-section of atherosclerosis©Getty

Microscopic cross-section of atherosclerosis

“Plaques with a weaker protein wall between the plaque and the inside of the blood vessel are more likely to burst,” says René Botnar, professor of cardiac imaging. “We aim to develop a reliable test, using a magnetic resonance imaging (MRI) scan, to detect those vulnerable plaques.”

The technique is based on a previous finding that high-risk plaques contain more of an unstable protein called tropoelastin. Botnar and colleagues have identified “biomarker” molecules that bind to tropoelastin. The next step is to link them to a chemical contrast agent that will show up plaques at highest risk of causing a heart attack in an MRI scan. “We will not be able to scan everyone with this technique but we can focus on people at high risk of heart disease,” Razavi says. People with dangerous plaques can then be given preventative medication or undergo surgery to insert stents that keep vulnerable blood vessels open.

A second project is developing technology to help surgeons operate on patients inside an MRI scanner, using the images for guidance. The procedure uses minimally invasive surgery to treat arrhythmias by introducing a catheter to destroy the small patches of heart tissue where abnormal electrical activity is causing an irregular heartbeat.

“We are transforming MRI scanning from a diagnostic to an interventional technique, while developing robotic guidance for the catheter,” Razavi says. A few more preclinical procedures will be performed on pigs before clinical trials begin.

The third cardiac imaging project involves building an ultra-detailed computer model of the heart, including its musculature and blood vessels, blood flow and electrical activity. The scans of an individual patient can be fed into the model, to produce a composite view far superior to one-off MRI or CT images.

“The generalised computer mesh of the heart is morphed to the patient data,” says Nic Smith, professor of biomedical engineering. The technology could improve treatment of cardiovascular diseases including heart failure, arrhythmias and abnormalities of blood flow.

Funding for the projects comes from a range of sources, including the UK research councils, the EU, the Wellcome Trust and the British Heart Foundation. At the same time the centre collaborates closely with industry, particularly Philips, the Dutch manufacturer of medical scanners. “We have three Philips employees here on site and a lot of what is developed here is put into their machines,” says Razavi. “We have to get our research into commercial products if we want it to be used widely by patients.”

. . .

A grassroots approach to flood control

A new hybrid grass could reduce flooding by enabling fields to absorb more water and so reduce the volumes overflowing into swollen streams and rivers during heavy rain.

Mike Humphreys, grass geneticist©Anthony Pugh

Mike Humphreys, grass geneticist

Tests in Devon, carried out over two years by scientists from a consortium of UK research organisations, show that the hybrid, called Festulolium loliaceum Prior, cuts the run-off from agricultural grassland by 40 to 50 per cent compared to the grasses commonly grown today. The results appear in the journal Scientific Reports.

Festulolium is a hybrid of two species commonly sown by British livestock farmers, meadow fescue (Festuca pratensis) and perennial ryegrass (Lolium perenne). Although many Festulolium varieties are known, Prior’s remarkable root growth gives it special defensive properties against flooding.

Mike Humphreys, grass geneticist at Aberystwyth University, says that when first sown or planted, Prior drives its roots very rapidly far into the soil. Then, once it is established, the deep roots die back and the grass lives on a network of shallower roots.

By thrusting deep underground and then retreating, the Festulolium roots leave a more porous, open soil structure, which can absorb more water than fields sown with other grasses.

Pine code

Norway spruce

Swedish scientists have sequenced the DNA of the Norway spruce, a mainstay of commercial forestry. It has one of the largest genomes known, seven times the size of ours.

The hydrological field trials, carried out at Rothamsted Research’s North Wyke station on the edge of Dartmoor, compared six grass varieties grown on identical plots measuring 10m by 3m, where rainfall and water run-off were monitored continuously.

Prior performed better than the other varieties at holding back potential flooding on 29 of the 33 occasions when there was run-off following heavy or prolonged rain. Overall its run-off was about half the level from plots with the other grasses.

Douglas Kell, chief executive of the Biotechnology and Biological Sciences Research Council, which is funding the project, says the Festulolium work exemplifies “the increasing recognition that the health and utility of plants can be greatly enhanced by improving below-ground traits such as root growth … I am sure that we shall see a continuing resurgence of interest in root biology, which findings such as this are sure to promote.”

Prior is also a good agricultural grass for feeding sheep and cattle, says Humphreys. The next step will be to carry out more extensive field trials on livestock farms across Britain. Farmers typically resow “improved grasslands” every five to 10 years. “Prior would easily last for 10 years,” Humphreys says.

Commercialisation of the variety will take place in collaboration with Germinal Holdings, the largest UK grass seed company, which has a long-standing partnership with Aberystwyth. But it will take at least five years to reach the market.

Meanwhile Humphreys is enthusiastic about the potential of other Festulolium grasses for different agricultural purposes. “We also have some drought-resistant varieties coming through,” he says. “There are field trials of Festulolium throughout Europe. They are very much the grasses of the future.”

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