Computer technology is enabling surgeons to reduce the risk of human error when using radiation to kill tumours.

It may also help doctors to treat tumours that could not have been treated before. It is possible to kill tumours using a device called a "gamma knife" which uses a combination of 201 radiation sources to blitz the tumour.

We're very excited by the idea of bringing uniformity to these treatment plans

Dr Michael Ferris, University of Wisconsin-Madison

But it can be difficult for doctors to bombard the tumour with radiation without the risk of damaging sensitive structures nearby.

The only way to strike an effective balance has been by drawing up a treatment plan based on a close analysis of scores of two-dimensional brain images.

In addition, surgery must be completed within 40 minutes, as the patient has to wear an uncomfortable head frame.

'Very exciting'

A new computer program is helping to automate and fine-tune this process - and reduce the risk of human error in setting radiation treatment plans.

Dr Michael Ferris, a computer scientist with the University of Wisconsin-Madison, US, is working with medical physicists and oncologists at the University of Maryland Medical School on the computer program.

He said: "We're very excited by the idea of bringing uniformity to these treatment plans.

"Now, if a patient is lucky, they will get a doctor who's been doing this for 15 years, rather than someone who just joined the programme. But with this computer program, both will be equally effective."

The computer program calculates how best to blitz the tumour so the minimum number of doses of radiation are needed to kill off every cancer cell.

'Three-dimensional problem'

Each cancer cell must receive at least 50% of the maximum dosage if the tumour is to be destroyed.

Dr Ferris said: "The mathematics involved is much better able to handle this three-dimensional problem.

"Doctors are trying to cover a three-dimensional target by just looking at many two-dimensional slices."

Another major benefit of the computer program is speed. It is able to map out a treatment plan in 20 minutes or less. Dr Ferris said the procedure also held the promise of treating larger tumours, those with irregular shapes, and those close to sensitive structures.

Dr Ferris presented his work to the annual meeting of the American Association for the Advancement of Science (AAAS) in San Francisco.