From Spitfire to surgery

Researchers are using a test devised in the 1930s, and used to gauge the stress on Spitfire superchargers, to model the stress that surgical procedures put on an aortic aneurysm.

Researchers at the University of Warwick have found a way of using a test devised in the 1930s, and used gauge the stress on the superchargers in spitfire fighter planes, to model the stress that surgical procedures would put on an aortic aneurysm. An aortic aneurysm is a dangerous bulge in the body’s largest artery, the aorta. The aorta is a crucial artery as it carries all the blood pumped from the heart.

Photoelasticity is a technique that has been used for decades in industry. It looks at the patterns of coloured light reflected from the surface of an object to gain a detailed understanding of the stresses on that object.

In its most modern incarnation photoelectric stress analysis uses high tech light sources and computer analysis to get an even more precise understanding of the stresses involved.

Mounting a piece of machinery on a test rig to perform tests is relatively simple. Using the same equipment to understand the stress on a part of the human body when the human is still using it is not so straightforward. Now researchers at the University of Warwick’s Warwick Manufacturing Group working with a surgeon at UCL have resolved the problem.

Initially surgeons had tried placing mechanical strain gauges on an aortic aneurysm as they manipulated it but found that the gauges themselves placed an unwelcome additional physical strain on the aortic aneurysm.

They turned to researchers at the University of Warwick led by Geoff Calvert who had an idea that would combine photoelastic stress analysis with the technology of rapid prototyping to solve the problem.

The University of Warwick and UCL researchers took a 3D scan of the patient’s actual aortic aneurysm and used rapid prototyping technology to produce an exact latex duplicate of the aneurysm. They then covered the duplicate with a reflective coating and used photoelastic stress analysis to examine the stress on the model aneurysm as the surgeon manipulated it.

“One of the exciting benefits of this technique is that it will actually allow surgeons to explore a greater range of possible interventions and manipulations of an aneurysm and get a clear picture of the stresses created without the obvious risks that testing less conservative interventions would bring if they were tried out on the actual patient,” said Dr Arindam Chaudhuri a heart surgeon carrying out research at UCL.

University of Warwick researcher Mr Geoff Calvert is seeking further funding to research materials that could be used in the rapid prototyped aortic aneurysm that would provide an even closer mimic of the mechanical properties of the original aortic aneurysm.

Mr Calvert is also looking for support to develop another technique that would stretch the ability of current photoelectric stress analysis equipment to draw on the more limited reflective properties of the original aortic aneurysm. This would provide surgeons with a real time monitor of the stress on the aneurysm as they operate.