At some point in our lives, most of us will require some kind of surgery. It is highly probable that this will be to identify and remove a cancerous tumour. Because tumours occur in soft tissue, they cause surgeons a bit of a headache. One of the reasons for this is that soft tissues move, distort and deform during surgery – in addition some operations require a very detailed picture of such tissues – and traditional imaging techniques are just too fuzzy.
Recently two different EPSRC-funded research projects have been tackling the problems of soft tissue imaging and surgery from contrasting perspectives. Their results may be about to revolutionise operations on soft tissue.
Over the last ten years, Professor Dave Hawkes, and his colleagues at King’s College London, have been developing ways to help surgeons see important details of the area they are operating on that would otherwise be obscured.
During an operation it is essential that the surgeon is aware of organs, blood vessels or nerve fibres that need to be avoided. Having a three-dimensional image of the area enables the surgeon to steer clear of such vital regions and yet still work close to them. In addition, if the surgeon is searching for a target, such as a tumour, the image indicates how far away it is.
Initially, Professor Hawkes and his team developed image guidance for surgery of tumours in the brain and base of the skull. By taking pre-operative Magnetic Resonance Image (MRI) and X-ray Computed Tomography (CT) scans of the patient before surgery, they were able to develop a three-dimensional representation of the area that the surgeon could follow during surgery on a computer screen. However, there was one drawback – the surgeon had to keep looking away from the operation and up at the screen. For surgeons doing delicate operations with a surgical operating microscope it was particularly difficult to hold an instrument in place, look away from the microscope and then re-focus on a computer screen.
To overcome this problem Professor Hawkes and a co-worker, Dr Philip Edwards, devised a way of inserting their 3D image into the microscope field of view. The modified surgical operating microscope, known as MAGI, displayed the image just where the surgeon was looking. In effect this means the surgeon can ‘see through’ the wound and body fluids and visualise the exact area they are operating on.
The MAGI system became extremely useful to neurosurgeons but it couldn’t be used for operations on wobbly soft tissues. MAGI relies on images taken before the operation to build-up the three-dimensional picture. By the time of the operation the soft tissue concerned is likely to have deformed and these images will no longer be accurate enough. Professor Hawkes decided to rise to the challenge of developing a system that could be used on soft tissue operations as well.
First Professor Hawkes needed to understand how soft tissue deforms and so he created a computer model of a specific area of soft tissue. Along with Dr Graham Penny and Jane Blackall, he built up a model of how the liver moves and deforms.
‘We chose to look at the liver because this is an area where surgeons could really benefit from a 3D image,’ says Professor Hawkes. ‘Searching for a tumour in this large, soft structure requires complex navigation within the tissue.’
They also felt that the liver was a realistic target to model as it is less mobile than other soft tissue areas. ‘It will be a long time before we can model areas like the bowel as the movement is just too complex,’ he explains.
Recently, methods have been developed whereby liver tumours are removed by an interventional operation, meaning that the body is not cut open. Instead the interventionist inserts a needle through the abdomen and into the tumour in the liver. Once the needle is in the centre of the tumour, the needle tip is heated by laser and the tumour cell is killed.
The problem with this process is that it is difficult for the surgeon to locate the needle in the tumour using ordinary two-dimensional slices from CT scans. Often the needle has to be repositioned a number of times to find the tumour, causing the patient discomfort and taking a long time.
During the last three years Professor Hawkes and his colleagues have managed to successfully model liver deformations to provide a 3D image. This has been phantom tested and more recently run alongside operations to remove tumours from the liver.
Early trials indicate that Hawkes and Penny’s 3D imaging has improved the accuracy of surgeons’ tumour location, making needle placement much easier and more precise. Next Professor Hawkes is going to start work using a similar method to model the lung and produce 3D images: ‘We aim to model the breathing cycle so that a radiotherapist can target lung tumours with radiation more accurately.’
Meanwhile, over at Cranfield University, Professor Ricky Wang is hard at work on a new technique to image soft tissue right down to the individual cells.
Currently potential cancer cells are analysed by taking a sample from the body tissue and looking at it under the microscope. Professor Wang hopes that his technique will give high-resolution images of soft tissue without the need for taking tissue samples. His technique relies on a new imaging technology known as optical coherence tomography (OCT). A light source is fired down a fibre optic cable and onto the tissue surface. ‘By measuring the intensity of the reflected light, the amount of scattering and the time delay, it is possible to build up a detailed picture of the structures in the upper 2mm of the tissue,’ explains Professor Wang.
This will be immensely useful for endoscopic examinations to identify cancers of the reproductive, gastro-intestinal and respiratory tracts. ‘Early diagnosis is much more likely if individual cancerous cells can be spotted,’ he says.
So far Professor Wang has shown that OCT is capable of imaging down to the sub cellular level and he is currently working with gastric surgeons at the North Staffordshire Hospital to start imaging human gastro-intestinal tissues. A miniaturised probe for in vivo studies is being constructed.
Both the King’s College and Cranfield groups have made significant breakthroughs in understanding the complexities of visualising soft tissue. The tools that result from research in this area could, in the future, prove as indispensable to a surgeon about to operate as anaesthetic or a clean scalpel.
This article was reproduced by kind permission of Newsline – the official publication of the EPSRC.