A medical test used to detect cancer may actually be contributing to the disease, research suggests.

CT scans, short for computerized tomography scans, make use of X-rays to generate highly detailed images of the body. They play a crucial role in both diagnosing and keeping track of various illnesses such as cancer and bone fractures. Furthermore, CT scans are employed to aid in surgical procedures and to assess the effectiveness of specific medical interventions.

However, there is little to no regulation of the scanners and radiation levels emitted can vary widely machine to machine. 

In 2009, researchers estimated high doses of radiation from CT scans were responsible for two percent of all cancers (or roughly 30,000 per year).

And ongoing research indicates as the number of CT scans increases, related cancers will likely rise.

CT scans can be life-saving tests, catching disease or bleeding early enough to be treated.

However, experts say they are sometimes overprescribed and performed unnecessarily, potentially because of the money-making opportunities for the hospitals, as the tests are very expensive, or out of doctors’ fears of missing a diagnosis and being sued. 

CT scans are used to diagnose and monitor cancers and bone injuries

The above shows the estimated percent lifetime risk of death from cancer that is attributable to the radiation from a single CT scan of the head

Dr Rebecca Smith-Bindman, a professor at the University of California-San Francisco medical school, is one of the researchers in the 2009 and ongoing study. 

She told NBC News: ‘It’s unfathomable. We keep doing more and more CTs, and the doses keep going up.’ 

Dr Smith Bindman said between two machines, one could be exposing patients to 10 to 15 times higher radiation doses than the other. 

She added: ‘There is very large variation and the doses vary by an order of magnitude — tenfold, not 10 percent different — for patients seen for the same clinical problem.”

About 93million scans are performed in the US every year, according to IMV, a medical market research company – and that number is rising. 

Radiation exposure is measured in millisieverts (mSv), which measures the amount of radiation absorbed by the body. 

People are exposed to small amounts of radiation every day from their background environment or through things like flying. 

A 2007 study published in the The New England Journal of Medicine said although the risks to one person from CT scans are not large, ‘the increasing exposure to radiation in the population may be a public health issue in the future.’ 

The study authors wrote cancers attributable to CT radiation may fall in the range of 1.5 percent to two percent. 

The 2009 study Dr Smith-Bindman was involved in looked at the radiation dose associated with the 11 most common types of CT scans performed on 1,119 adult patients in 2008. 

Radiation exposure varied widely. Average doses ranged from 2 mSv for a head CT to 31 mSv for an abdominal and pelvic CT. 

For comparison, A roundtrip flight between New York and Tokyo exposes a person to 0.19 mSv. An x-ray of the stomach emits 0.6 mSv.

However, the researchers found the amount of radiation emitted by CT scanners varied widely across the four hospitals they collected data from – with a 13-fold difference between the highest and lowest doses for each scan type.

The team then estimated cancers resulting from CT scans based on age and sex of the patient.

About one in 270 women and one in 600 men who underwent a CT scan of arteries near their heart at 40 years old will develop cancer from that scan. 

The above shows the estimated percent lifetime risk of death from cancer that is attributable to the radiation from a single CT scan of the abdomen

About one in 8,100 women and one in 11,000 men who had a routine head CT scan at 40 will develop cancer from that scan.

For patients in their 20s, the risks were about double, and for patients in their 60s, the risks were halved. 

The researchers did not mention what type of cancer the patients may develop.  

Cancers that have previously been linked to radiation include leukemia, breast, colon, bladder, stomach, ovarian, lung and liver cancers, according to the US Nuclear Regulatory Commission.

The team concluded: ‘Radiation doses from commonly performed diagnostic CT examinations are higher and more variable than generally quoted, highlighting the need for greater standardization across institutions.’ 

CT scans are life-saving medical scans, but they are not without risk. 

In an attempt to tackle the problem, new Medicare regulations effective this year will require hospitals and imaging centers to collect and share information about the radiation emitted by their scanners.

The regulations also require a more careful inspection of the dosing, quality and necessity of CT scans. 

The new rules, issued in the final weeks of the Biden administration, are being rolled out over three years in hospitals and outpatient clinics and providers could face fines if they do not comply, beginning in 2027.

The Trump administration has not commented on its plans to follow, revise or reverse the new policies.