Heart patients might be prone to developing cancer due to radiation exposure caused by the increasing number of diagnostic imaging tests, including X-rays and CT scans they undergo, a study said.

Researchers from Columbia University Medical Center and New York-Presbyterian Hospital in New York found that myocardial perfusion imaging is a major source of radiation caused from medical imaging. They were curious to know how much of these scans add up to the risk of getting cancer.

From 1990 to 2002, researchers noted that the number of myocardial perfusion scans have increased from 3 million to 9.3 million. They studied the data of more than 1,000 patients treated at Columbia University Medical Center in 2006.

They found repeat heart scans to be very common. About 18.2 per cent of them took at least three MPI scans and 5 per cent had to take five such scans. Researchers note that a radiation dose of 50 millisieverts starts to raise concerns about health and a dose of 100 millisieverts might raise the risk of cancer. Radiation is measured in millisieverts.

According to the US Food and Drug Administration, a CT scan delivers 1 to 10 millisieverts of radiation.

Researchers noted that about 6.5 per cent of the participants got increasing doses of more than 100 millisieverts from the heart scans alone, and 31.4 per cent got more than 100 millisieverts from all medical sources.

Doctors and researchers have concluded that patients and doctors should keep a check on the number of such tests taken, in order to prevent long-term cancer risks.