The radiation produced by CT scans performed in 2007 will cause 29,000 cancers and kill 14,500 Americans, according to a study published in the Archives of Internal Medicine.
To reach this conclusion, Amy Berrington de Gonzalez and colleagues from the National Cancer Institute used a computer simulation to estimate the impact of the 70 million or so CT scans that were performed in the US that year (only 3 million were performed in 1980).
The scientists estimated that about a third of the future cancers will occur in people who were between the ages of 35 and 54 when they received their CT, and 15% of them will develop in people who were children or teens when the scan was performed.
About two-thirds of the new cancers will develop in women, since they are more vulnerable to radiation.
“There is a significant amount of radiation with these CT scans, more than what we thought, and there is a significant number of cancers,” Rita Redberg, the editor of the Archives of Internal Medicine, told the LA Times.
“While certainly some of the scans are incredibly important and life saving, it is also certain that some of them were not necessary,” Redberg added.
CT scans provide pristine images by combining data from multiple x-ray images. They can also expose patients to up to 400 times more DNA-damaging radiation than conventional chest x-rays.
In another study, Rebecca Smith-Bindman and colleagues from UCSF found that radiation exposure varies almost 13-fold for different kinds of CT studies, from about 2 millisieverts for a routine head CT scan to 31 millisieverts for a scan of the abdomen and pelvis.
The average American receives about 3 millisieverts of radiation per year, a level not considered to be a health risk.