There are currently no fail-safe methods to test for the illness which affects around 500,000 people in Britain. But researchers in Japan have developed a scan which could eventually help doctors accurately diagnose the disease.
The technology allows them to detect a protein called tau which builds up in the brains of people with Alzheimer's.
Dr Eric Karran, director of research at Alzheimer's Research UK, said: "If this method is shown to be effective, such a scan could also be a useful aid for providing people with an accurate diagnosis, as well as for monitoring disease progression. Larger and more long-term studies are needed to confirm these findings."