An advisory committee to the US Food and Drug Administration has approved a new brain scan procedure for detecting Alzheimer's disease, as long as doctors receive additional training to use it.

The process involves injecting a chemical called Amyvid, made by US pharmaceutical giant Eli Lilly, followed by an imaging scan that can detect plaque, or beta-amyloid aggregates, that indicate the presence of Alzheimer's.

The FDA expert panel, whose rulings the FDA does not have to follow but typically does, first voted against approving (13 against and three in favor) the test in their meeting on Thursday.

But the panel inserted a condition that was not presented by the FDA - that a training program would be implemented that shows accurate diagnosis can be made in the general population - and approved that unanimously, 16-0.

Earlier this week, a study published in the Journal of the American Medical Association said the molecular imaging procedure could help lead to better treatment and diagnosis of Alzheimer's in living patients.

There is no cure for the degenerative brain condition that affects around five million Americans.