The scan was taken after Collins, nicknamed the "Celtic Warrior", collapsed when sparring in an East End gym 11 days ago. Yesterday Collins said: "Donal Shanahan, the consultant surgeon who did my test, said that scar tissue from a previous injury had probably hardened, and the scar is sandwiched between the grey matter of the brain and skull.
"Impact on that part of my head could kill the cells. His advice was not to box again for fear of damage.
"I can lead a perfectly normal life, but because of the nature of boxing, I could not avoid receiving punches to that part of my head.
"The headaches I was experiencing in training were a warning. That's why I had the brain scan."
Collins, who retired as undefeated World Boxing Organisation super-middleweight champion in October 1997, decided to return to the ring 16 days ago, his main objective being to challenge the American Roy Jones, the World Boxing Council light-heavyweight champion.
He was also due to meet Joe Calzaghe, the current WBO super-middleweight champion, and had been pencilled in for a supporting bout when the Welshman defends his title against Australian Ricky Thornberry at Cardiff on June 5.
Collins broke into the big time when he won the WBO middleweight championship from Chris Pyatt in May 1994. He vacated the title and ended Chris Eubank's unbeaten record when he captured the WBO super-middleweight crown from the Brighton boxer in March 1995.