A robot to roam the brain

All in the head: THES reporters investigate the latest advances in brain surgery

The Fraunhofer Institute for Biomedical Technology at St Ingbert in Germany is coordinating the development of a robot to guide surgeons performing keyhole brain surgery.

The project involves partners in Germany, the United Kingdom, the Netherlands, France, Switzerland, Austria and Denmark. The scientists aim to develop a system for operations, initially to remove hollow tumours, such as cysts, moving on to malignant tumours.

Keyhole surgery involves inserting an endoscope, a tube a few millimetres in diameter that holds the surgical instruments, into the body and guiding it to the site.

Endoscopes, however, are difficult to handle and give a restricted view. The brain may move during an operation, which makes it difficult to determine the probe's exact position. This, together with involuntary movements by the surgeon, can lead to healthy tissue being inadvertently damaged.

The project aims to combine ultrasound imaging, computer technology and robotics to make keyhole brain surgery more user-friendly and safer for the patient.

Ultrasound imaging will be used to screen operations. Other methods that give a three-dimensional image are very expensive or can only be used for short periods. Ultrasound is commonly used to monitor pregnancies, but it cannot penetrate the skull.

The team at St Ingbert will try to overcome this by placing a device the size of a coin just inside the skull for the surgery's duration. The device will send and receive ultrasound signals and, as with X-ray pictures in CT scanning, a computer will form a 3-D image. Surgeons will see the actual position of the instruments and the tissue while operating.

Before the operation doctors perform a CT scan, which lets them see the position of the cyst or tumour. They then determine a path for inserting the instruments. Researchers want to feed this data to a computer that controls a robot attached to the endoscope. Should the surgeon stray from the prescribed path or be in danger of leaving the target region, the robot will slow the endoscope's movement and eventually stop it.

Brian Davies, reader in robotics, heads the mechatronics in medicine group at the department of mechanical engineering, Imperial College, London. Together with Fokker Control Systems in the Netherlands, it will provide the robotics for the roboscope.

Surgeons using the device will still feel when they are pushing against tissue. But when approaching healthy tissue, the movement will become stiffer before stopping altogether. This effect depends on a server combining complicated mechanics and computer control.

During surgery a computer continuously updated on the endoscope's position will compensate for brain movements, and the mechanics will ensure an even resistance to motion in the area.

Because of the complexity required, the scientists have to build the mechanism specifically for the roboscope even though they can use some concepts known from an experimental knee surgery robot they constructed.

According to Dr Davies, Germany uses a small number of robotic systems for hip surgery, but there are none in Britain yet. The international team hopes to be able to present a prototype in two years. If they find further funding, they aim to complete a commercial prototype after one more year.