Pioneering brain imaging that can detect the build-up of destructive proteins linked to Alzheimer's has been developed by Japanese scientists.
It could lead to new ways of diagnosing the condition and of testing the effectivenewss of new drugs.
The technology, reported in the journal Neuron, can identify inside a living brain clumps of a protein called tau that is closely linked to the disease.
Alzheimer's Research UK said it was promising work.
Alzheimer's disease is a problem for researchers trying to come up with a cure. The brain starts to die years before any symptoms are detected, which means drugs are probably given too late.
A diagnosis of Alzheimer's cannot be made with absolute certainty until a patient has died and their brain is examined. It is also not 100% clear what is the cause of the dementia and what are just symptoms.
One protein, called tau, is very closely linked to the disease, with tangles of tau thought to be one way in which brain cellls are killed.
The team, led by the National Institute of Radiological Sciences in Chiba, used positron emission tomography to build a 3D picture of tau in the brain.