One hemisphere of a healthy brain on the left is pictured next to one from a person who had Alzheimer's disease.
If it was full of the plaques and tangles characteristic of the disease, then that person had Alzheimer's.
Plaques form when the protein amyloid-beta builds up in the brain. In healthy people, amyloid is swept away. But in Alzheimer's patients, it accumulates like garbage.
And now imaging tools are getting so good that we can see plaques and tangles in the brain while people are still alive. This could make diagnosis even better.
More than 5 million people in the US have Alzheimer's today, and this number is going to keep rising as the population ages. Over 13 million Americans are expected to have the disease by 2050. Getting their diagnosis right is the first step to tailoring treatments.
General Electric (GE) developed a tag that latches on to beta-amyloid in the brain, which the FDA approved in 2013. It can show plaque formation with a brain scan.
The University of Pittsburgh invented a similar compound:
This image shows a PET scan of a patient with Alzheimer's disease on the left and an elderly person with normal memory on the right. Areas of red and yellow show high concentrations of Pittsburgh compound B, which binds to amyloid-beta, in the brain.
But the Alzheimer's Association cautions that these scans aren't accurate enough to be used on their own yet.
Because amyloid plaques can form in patients decades before they actually develop Alzheimer's disease, the Association suggests using PET imaging techniques only in conjunction with other diagnostic tests.
Since the plaques form so early, detecting them with these imaging techniques could one day help us slow the progression of the disease or even prevent it. Today, that's a long way off. There are currently no treatments that stop the progression of Alzheimer's, so detecting it early is of only limited value.
But in the future, that might be different. If we can see the plaques that are causing the problems, doctors imagine we might someday be able to watch as drugs that have not been invented yet shrink them. And we could watch an Alzheimer's brain turn back into a healthy brain.