12-year hall of fame career or during his four seasons in college, but he's one of nine former nfl players who have had a new brain scan that may help identify chronic traumatic encephalopathy or cte, a brain disease caused by head trauma linked to dementia and depression. dorsett says he's tested positive for symptoms consistent with cte. previously, the only way to find out if someone had cte was after their death, with an autopsy on the brain. now -- >> this test involves a tracer which is injected into a vein and then it will bind to these abnormal proteins that we see in cte so if you have them in your brain, it can diagnose this in the living person. >> reporter: neurosurgeon julian bailes, former physician for the pittsburgh steelers, is part of a team that devised the new brain scan. he acknowledges it's too early to tell if this test is reliable. the sample size is too small, he says, and the results need to be peer reviewed. it's believed cte played a role