New Delhi: Repeated exposure to unnecessary computed tomography (CT) scans raises the risk of cancers as with alcohol consumption and obesity, according to a new study. 

The study, led by researchers from the University of California-San Francisco (UCSF), showed that CT scan radiation accounts for 5 per cent of all cancers annually. 

Infants, children, and adolescents are at high risk of cancers, with those under 1 year most at risk. Besides children, adults are also at risk, since they are the most likely to get scans, said the team, cautioning against overusing and overdosing on CTs.  

The most frequently projected cancers in children due to CT scan radiation include thyroid, lung, and breast, while in adults it was cancers of the lung, colon, leukaemia, bladder, and breast. 

"CTs can save lives, but its potential harms are often overlooked," said Rebecca Smith-Bindman, a UCSF radiologist. 

“The study estimates put CT on par with other significant risk factors, such as alcohol consumption and excess body weight," she added.  

In the study, appearing in the JAMA Internal Medicine, the team said that nearly 103,000 cancers are predicted to result from the 93 million CTs that were performed in 2023 alone.  

This is three to four times more than previous assessments, the researchers said. 

"Reducing the number of scans and reducing doses per scan would save lives," said Smith-Bindman. 

CT is both indispensable and widely used to detect tumors and diagnose many illnesses. But, CTs expose patients to ionising radiation -- a carcinogen -- and it's long been known that the technology carries a higher risk of cancer. 

The study is based on estimates of the total number of lifetime cancers associated with radiation exposure concerning the number and type of CT scans performed in 2023. 

Researchers analysed 93 million exams from 61.5 million patients in the US.  

The number of scans increased with age, peaking in adults between 60 to 69 years old. Children accounted for 4.2 per cent of the scans. (IANS)