By Bethany Bell
BBC correspondent in Vienna
Experts at the UN's nuclear agency have warned that patients worldwide are suffering from radiation burns because doctors have not been properly trained.
Patients receive radiation doses up to 1,000 times that of a chest X-ray
Cardiologists meeting in Vienna at the International Atomic Energy Agency have been learning ways to prevent burns.
Experts say heart patients are at risk during procedures such as angioplasty, in which a tube is passed through blood vessels to open blocked arteries.
This procedure and others like it require constant X-ray monitoring.
That results in radiation exposure that is around 1,000 times more than a standard chest X-ray.
Lewis Wagner, professor of radiological physics at the University of Texas, says most cardiologists have no idea the procedures they perform can cause severe and extremely painful radiation injuries.
There are no worldwide statistics on the number of such burns, but about one case a month is turning up in courts in the United States.
The doctors gave a rough estimate of one severe burn in 10,000 procedures.
Around a million angioplasty procedures are performed worldwide every year.