London: British scientists claim that a brain scan could help detect the early signs of Alzheimer's disease, the most common form of dementia, in under an hour.

A team at Manchester University has discovered that a positron emission tomography (PET) scan, usually used to spot cancerous tumours, can diagnose dementia in people by measuring their brain activity.

For their research, the scientists analysed 44 healthy people - 40 with Alzheimer's disease and 94 others with mild cognitive impairment (MCI).

In the healthy group the scan showed high levels of brain activity by measuring the amount of glucose being used by the cells in the brain. But those with MCI and Alzheimer's the activity was reduced, reports said.

The scientists believe it will give doctors conclusive proof that a patient is set to develop Alzheimer's. At present patients undergo some six months of memory tests before they can receive any results about their condition.

Prof Karl Herholz, who led the research, said this could rapidly speed up the process of finding a drug to stop the disease progressing. "The scan takes 10 to 20 minutes and the evaluation takes 30 minutes," he said.