Eli Lilly and Co. says it has won approval from the U.S. Food and Drug Administration for a new imaging agent that could help physicians better diagnose Alzheimer’s disease and other forms of dementia.

The agent, called Amyvid, is not expected to produce high-dollar sales for Lilly, but it could help to identify patients with Alzheimer’s—and those without it—earlier than other methods, perhaps improving treatment and focusing research efforts.

Indianapolis-based Lilly is currently studying an experimental treatment for Alzheimer’s disease, solanezumab, which if successful, could become a multibillion-per-year blockbuster and reverse Lilly’s recent struggles with expiring patents on its older blockbuster products. No treatment exists that slows or reverses the progression of Alzheimer's disease, which currently afflicts about 30 million people worldwide and is expected to afflict three times that number by 2050.

However, even Lilly officials say the chance of the solanezumab's success is low. That’s because scientists do not completely understand what causes Alzheimer’s disease. So efforts by Lilly and other major pharmaceutical companies to develop treatments is based so far on unproven theories.

Lilly’s scientists have followed the theory that Alzheimer’s is caused by the buildup of the protein beta-amyloid in a patient’s brain, which eventually forms sticky plaques that impede brain function. Solanezumab binds to amyloid in an effort to remove it from the brain via the bloodstream. And the imaging agent Amyvid binds to amyloid plaques, making them detectable using a PET scan.

Previously, the presence of amyloid plaques could only be confirmed by an autopsy, after a patient’s death. And sometimes the diagnosis of Alzheimer’s was proved wrong.

"It's estimated that one in five patients clinically diagnosed with probable Alzheimer's Disease during life do not end up having Alzheimer's Disease pathology upon autopsy," said Dr. Daniel Skovronsky, CEO of Avid Radiopharmaceuticals Inc., the company that developed Amyvid, and which Lilly acquired in 2010 for $300 million. "The approval of Amyvid offers physicians a tool that, in conjunction with other diagnostic evaluations, can provide information to help physicians evaluate their patients."

Amyvid will become available in limited supplies in June. The FDA approval comes more than a year after the agency was first scheduled to make a decision on the drug.