It's been called the “holy grail” of brain research and now, it may have been found.

U.S. scientists say they have developed a way to detect the concussion-related brain disease called CTE, or chronic traumatic encephalopathy, in living athletes.

Until now, the disease, which may bring on dementia, depression and personality changes, could only be confirmed through an autopsy.

Now for the first time, researchers at the University of California, Los Angeles have figured out how to use a brain-imaging tool to identify the abnormal build-up of tau proteins -- the key marker of CTE -- in people showing early signs of the disease.

"Early detection of tau proteins may help us to understand what is happening sooner in the brains of these injured athletes," lead author Dr. Gary Small said in a statement.

Small is UCLA's Parlow–Solomon Professor on Aging and a professor of psychiatry and biobehavioral sciences at the Semel Institute for Neuroscience and Human Behavior at UCLA.

"Our findings may also guide us in developing strategies and interventions to protect those with early symptoms, rather than try to repair damage once it becomes extensive."

The preliminary findings are reported in the latest online issue of the American Journal of Geriatric Psychiatry.

A total of 34 former NFL players have been diagnosed with CTE after their deaths. It’s also been found in a handful of former NHL players, including former Buffalo Sabre Rick Martin, who died last year at the age of 59. CTE was also discovered in the brain of former NFL linebacker Junior Seau, who committed suicide last May at the age of 42 by shooting himself in the chest.

More than 4,000 former NFL players are currently suing the league in U.S. federal court, alleging the league knowingly failed to protect players for decades from the long-term effects of concussions.

For this latest study, the researchers recruited five retired NFL players aged 45 or older, had a history of one or more concussions, and were beginning to show cognitive or mood problems. One of them was former backup quarterback Wayne Clark, 65, who sustained at least three concussions in his career, including two in the NFL.

The UCLA researchers injected the players with a newly created dye containing a radioisotope, called FDDNP, which binds to deposits of amyloid beta "plaques" and tau "tangles.” They then scanned the men’s brains with a PET scanner, designed to detect radiation.

The idea was the more tau plaques the men had in their brains, the more the FDDNP would bind to it and be picked up by the PET scans. The researchers also took scans of equivalent healthy men to compare the results.

They found the NFL players who had experienced a greater number of concussions had higher FDDNP levels than the healthy men. As well, they also had higher levels of FDDNP in the regions of the brain that control learning, memory, behaviour, emotions, and other mental and physical functions.

"The FDDNP binding patterns in the players' scans were consistent with the tau deposit patterns that have been observed at autopsy in CTE cases," said study author Dr. Jorge R. Barrio, a professor of molecular and medical pharmacology at the David Geffen School of Medicine at UCLA.

The UCLA team is excited by their findings and say this is the first -- and only -- imaging marker that can measure tau proteins in living humans. They say creating a way to detect CTE early is a critical first step in developing way to prevent CTE progression.

Canadian neurosurgeon Dr. Charles Tator, the head of the Canadian Sports Concussion project at the Krembil Neuroscience Centre at Toronto Western Hospital, was not involved in the research but says it could be a game-changer for CTE research.

“This is a significant improvement on our ability to diagnose the ravages of concussion like CTE,” he told CTV’s Canada AM Wednesday. “…This new agent looks like it will help us considerably.”

The UCLA team notes larger followup studies are needed to understand how useful it will be to be able to detect tau proteins early. But Tator says it’s possible that one day, the imaging test could be given to those who have had a number of head injuries and who might be at risk of developing CTE.