EDINBURGH University researchers say they have discovered a way of predicting who is at greatest risk of a heart attack.
They used PET-CT scanners, which are used in major teaching hospitals, to detect fatty blockages in the heart.
There is currently no way of predicting who will be affected other than by making general assumptions based on lifestyle and family history.
PET-CT scanners combine two types of scanning techniques to produce accurate images of the body.
CT scans show the structures of the heart. PET scans show up blood vessels where the body is healing itself in response to injury.
Researchers studied the hearts of 80 volunteers who had already suffered a heart attack or were suffering from angina - putting them at high risk of an attack.
Writing in the Lancet, they said that the fatty plaques, which cause heart attacks, showed up as bright yellow in the scans.
About 90% of patients who had already had a heart attack had a lit-up area in one of their blood vessels.
About 40% of patients with angina had a plaque which lit up yellow, suggesting a heart attack may be imminent.
If the technique is proved effective, the researchers said it would be the first time medics had been able to accurately predict who was in danger.
They could then be treated with drugs or surgery. Heart disease kills about 8,000 people every year in Scotland.