One of the biggest problems with Alzheimers is the inability to directly diagnose the disease. The only sure way is autopsy, which is understandably a sub-optimal situation when you're trying to determine if treatment is needed.

However, according to this New Scientist article, such drastic measures may no longer be needed:

Takaomi Saido at the Riken Brain Science Institute in Wako, Japan, and his colleagues, have developed a new, non-toxic tracer that attaches itself to the amyloid plaques in the brain and can be detected by regular MRI scanners. The tracer is made from a form of fluorine that is a common additive in drinking water, and a form of hydrogen, which is known to bind to amyloid.

The technique is immediately useful in primary research, which uses special mice to examine disease progress and treatment effectiveness. The tracer works in human tissue, although no trials involving living humans have been initiated.

By detecting the disease before symptoms are exhibited and monitoring its progression after treatment, this technique should have profound implications in the fight against this tragic disease.