On May 3, AIIMS director Dr Randeep Guleria warned against unnecessary CT scans by patients having mild Covid-19 symptoms and said overuse of CT scans increases exposure to radiation which in turn escalates the risk of cancer.

He said one CT scan is equivalent to 300-400 chest X-rays and this increases the risk of having cancer in later life, especially among the youth, as one is exposed to harmful radiation. “If you are in doubt, then go for a chest X-ray first. If necessary, the doctor will give proper advice whether a CT scan is needed or not,” Guleria had said.

Computed tomography, also known as computed axial tomography or CT scan, is a tool doctors use to diagnose several types of health problems. It creates images of structures inside your body which helps doctors get a look at your internal organs and then advise further treatment. A CT scan exposes your body to some radiation that involves an amount of risk.

Dr Guleria is not the first doctor or expert who cautioned against the misuse or dangerous effects of CT scan which may lead to cancer.

According to Harvard Health, the scans expose people to X-rays, and this so-called ionising radiation can damage cells and lead to cancer down the road. In one of its reports, it said most of the increased exposure in the United States is due to CT scanning and nuclear imaging, which require larger radiation doses than traditional X-rays. A chest X-ray, for example, delivers 0.1 mSv, while a chest CT scan delivers 7 mSv — 70 times as much.

In another report, while describing about the risk, Harvard Health said the body regions where CT-related cancer is most likely to occur are the chest, abdomen, and pelvis, where faster-growing cells are more vulnerable to radiation. The lifetime risk posed by a single abdominal CT of 8 mSv is calculated to be 0.05 per cent, or one in 2,000 chance of developing cancer.

A report by the Yale School of Medicine said each CT scan exposes patients to between 100 and 500 times the amount of radiation in an X-ray. WebMD, one of the leading sources for trustworthy and timely health and medical news and information, says one chest CT scan delivers the same radiation amount as 100-200 X-rays.

Much like Harvard, the National Cancer Institute (NCI) of the United States estimates that the additional risk of developing a fatal cancer from a CT scan is one in 2,000. While a single scan would rarely be concerning, multiple or unnecessary repetitive CT scans without doctors’ prescription is very hazardous and may increase the risk of developing a cancer in the near future.