Originally Published 04 August 2004

A test devised in the 1930s to gauge the stresses of superchargers on wartime spitfire fighter planes has recently been used to measure stress of a different kind. Researchers at the University of Warwick have found a way of using the photoelasticity test to model the stress of surgical procedures on an aortic aneurysm. An aortic aneurysm is the dilatation (widening or bulge) of a portion of the aorta. If an aortic aneurysm becomes very large it can rupture and burst leading to internal bleeding which is often fatal.

Photoelasticity was initially developed to apply optical principles to solve engineering problems of elasticity. Stress analysis involves using high tech light sources and computer analysis to get a precise understanding of the stresses present in a material. Now researchers at the University of Warwick’s Warwick Manufacturing Group (WMG) working with a surgeon at University College London (UCL) have found a way of measuring the stress on an aortic aneurysm.

Surgeons at UCL turned to researchers at the University of Warwick after finding that the mechanical strain gauges they placed on an aortic aneurysm resulted in additional physical stresses to the aortic aneurysm. Researchers at Warwick, led by Geoff Calvert at WMG, combined photoelastic stress analysis with rapid prototyping technology to allow the surgeons to measure the stress and strains whilst dealing with aortic aneurysms. The University of Warwick and UCL researchers took a 3D scan of the patient’s actual aortic aneurysm and used rapid prototyping 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.

Dr Arindam Chaudhuri a heart surgeon carrying out research at UCL said:

“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.”

Geoff Calvert is now 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. He 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 which would provide surgeons with a real time monitor of the stress on the aneurysm as they operate.

Mr Geoff Calvert, Warwick Manufacturing Group University of Warwick 024 76575436 mobile 0777 3800769 g.c.calvert@warwick.ac.uk