Scanning with robots

Mechatronic MRI ‘surgeon’ could improve accuracy of prostate cancer biopsies.

A robot surgeon that can be attached to an MRI scanner to improve the accuracy of prostate cancer biopsies is being developed for the National Health Service.

Engineers at ImperialCollege’s mechatronics in medicine laboratory are developing the master/slave robot system to allow biopsies to be taken within the cramped conditions of an MRI chamber, in a two-year project funded by the Department of Health.

This will allow surgeons to carry out biopsies using the much more detailed images produced by MRI scanners, rather than the fuzzy ultrasound pictures used at present, improving their accuracy.

Prostate cancer is the most commonly diagnosed cancer in men in the UK, and the second biggest male cancer killer after lung cancer.

The project is being funded under the NHS Prostate Cancer Programme, which was launched in 2000, in an effort to expand research into the condition and improve treatment.

To detect prostate cancers, surgeons carry out biopsies guided by ultrasound probes. but the image quality is poor, making it difficult to specifically target the affected area to take a sample.

The only way to significantly improve the quality would be through the use of MRI, but space in the chambers is extremely limited, making it impossible for surgeons to get inside to carry out the procedure, said Dr Alex Zivanovic, research associate in the laboratory, which is based in the department of mechanical engineering.

So the researchers are developing a system in which a master robot outside the scanner, and operated by the surgeon, controls a slave unit inside the chamber.

However, the extremely strong magnetic fields generated by MRI scanners rule out the use of motors to operate the robot.

So instead the team is investigating the use of piezo-ceramic actuators, which deflect when a voltage is applied to them allowing them to ‘walk’ along a surface, and are not affected by the magnetic fields.

The robot is limited in its freedom of movement to protect the patient, said Zivanovic. ‘We are designing it to be intrinsically safe. It is limited in its range of motion, so that if something goes wrong it can’t move outside that range,’ he said.

The technology could also be used for other biopsies and procedures, said Zivanovic.

The project is due to be completed in 2006. The researchers have settled on a design for the master robot, and have come up with initial ideas for the slave, which they plan to develop further.