Scientists at the University of Limerick are perfecting a means of putting medical implants through their paces on a computer before they reach the patient. Three-dimensional models of diseased blood vessels are being "made" in computers by using highly detailed images of patients taken with Magnetic Resonance Imaging (MRI) scanners. Using these models, scientists can try out a surgical treatment such as a heart by-pass graft and check how well the blood flows.
Any number of positions and designs of graft can be tested and tailored to the individual patient to find the best results. The surgeons performing the by-pass can then be advised how to proceed. The perfection of this technique will bring major benefits for sufferers of cardiovascular disease.
"In the not too distant future, surgeons will bring their surgical implant problems to us," said Dr Tim McGloughlin of the Biomedical Engineering Research Centre at UL. "We will do an MRI scan of the patient and from that do a complete computational assessment of the geometry of that patient. We then suggest to the surgeon how to tailor the operation."
Cardiovascular disease in its most common form is the gradual clogging of blood vessels by fatty materials. The vessels eventually become so narrowed that the flow of blood and vital oxygen to cells is cut off, leading to organ failure; blood clots that block the flow entirely are a constant risk. Most commonly affected are arteries to the heart, brain, kidneys, eyes and legs. The disease is one of the biggest killers in Ireland today.
To cure the problem, surgeons perform an operation where the blocked artery is by-passed by implanting a blood vessel graft or length of artificial tube.
To work properly, the implant has to be in the best possible position to restore the correct blood flow. This will vary from patient to patient depending on which vessel is faulty and where.
Dr McGloughlin and his team use a computer to simulate the flow of blood around the flexible vessels and the surgical implant by a method borrowed from aerospace engineers called computational fluid dynamics.
Originally developed to calculate the movement of air across the surface of an aircraft, the fluid dynamics calculations allow a map to be drawn of blood flow rates through the virtual vessels.
From this, the most effective position for the implant can be found.
"In blood vessel work it is not uncommon to use artificial materials. We can model these synthetic materials in situ, measuring their response to pressure," said Dr McGloughlin.
A wide variety of medical implants is available, and at present the surgeon decides which to use. The team at UL have found that the performance of these implants varies from patient to patient. Some may work for 10 years, but others need replacement after five.
The work of the UL team will increase the lifetime of implants by using the modelling to find the one most suited to a patient's particular needs.
"We're introducing more engineering into the equation and will enhance the quality of the treatment by a more scientific approach," said Dr McGloughlin.
Recently, Dr McGloughlin has teamed up with the department of Biomedical Engineering at Georgia Institute of Technology in Atlanta. A grant from Enterprise Ireland allowed a student from UL to travel to the institute, which is situated in the "Silicon Valley" of biotechnology. The UL team is working on the creation of the computational models with the Georgia team while making use of its MRI facility.
A further boost to the team's efforts came recently with the announcement of Health Research Board funding for UL to buy an MRI scanner.
The link with Georgia is also exposing the UL team to the new science of tissue engineering, which could lead to the manufacture of implants made not from artificial materials but from human tissues using stem cell technology.
Dr Peter Foote is a research scientist working with BAE Systems of Bristol. He is a participant in the Media Fellow programme organised by the British Association for the Advancement of Science.