Model medicine

A virtual-reality training device that uses force-feedback and 3D imaging to recreate complicated invasive medical procedures is the subject of a collaborative research project co-ordinated by Wales University, Bangor.

The university is working alongside the medical imaging team at Liverpool University and with researchers at Hull, Imperial College, London and Leeds University to develop the innovative device that will be used to help train interventional radiologists perform delicate ‘pinhole’ surgery.

Interventional radiology (IR) is a relatively new discipline that uses the latest imaging technology together with miniature needles to treat problems such as blocked arteries.

The most common procedure is angioplasty, in which a guidewire is passed along an artery and a tiny balloon inflated to ease a blockage. While the procedure uses ultrasound to follow the wire’s progress interventional radiology also requires an extremely high level of skill and a fine sense of touch.

Professor Nigel John, project leader from Wales University’s School of Informatics, said an extremely realistic virtual reality simulator could be used not just by IR students but would also allow qualified practitioners the chance to practice unusual procedures before being let loose on real patients.

‘We want to have a physics-based simulator that will allow an interventional radiologist to train in the typical procedures including needle puncture, insertion of a guidewire and catheter into arteries. It’s a job that requires a very good sense of touch and while there are some commercial products available, they are very limited,’ said John.

Existing virtual reality training packages only contain a fixed number of possible training procedures and the simulated body is a generic model that differs greatly from the actual physiology of the prospective patient. The research team aims to use CT scans, which can be used to create 3D models that exactly match the patient’s body.

John said they also hope to use the scan to infer from it other aspects of the patient’s physiology. For example, a blocked or diseased artery would be much stiffer than a healthy artery. This information could be used to change the feel of the tools in the surgeon’s hand through the use of haptic devices that provide force-feedback to accurately reproduce the experience of the real-life procedure.

Preliminary work at the university has resulted in two force-feedback joysticks — developed by SensAble Technologies — that can replicate the feeling of the actual tools used by an interventional radiologist.

‘As you insert a virtual needle it really does feel like you are pushing through skin and then through the different tissue types as you move the joystick through the virtual patient,’ said John.

Researchers at Hull University are developing another haptic device that can accurately mimic a pulse. This is because radiologists also use a patient’s pulse — as well as ultrasound — to identify the correct place to insert the needle.

Surgeons would wear a virtual reality headset on to which would be projected the 3D model of the body with the array of haptic devices laid out before them.

To heighten the accuracy of the haptic devices, surgeons at the Royal Liverpool Hospital are also going to take force measurements using pressure sensors during a live surgical procedure. This data will then be fed back into the haptic software model for added realism.

For John, one of the trickiest aspects of the project is likely to be the accurate, real-time representation of all of the physiological elements of the virtual patient including breathing, blood flow and the way in which the tissue deforms under pressure, all of which will require the development of complicated software.

3D specialist Virtalis is acting as a consultant on the project and will help to bring the end product to commercialisation when the project ends in mid-2010.

Every six months a prototype will be deployed at the hospital for the interventional radiologists there to give their feedback on its progress, said John.

He added: ‘There are so many challenges left but if it’s successful this will be one of the most sophisticated training virtual environments around.’