Can CT Scans Give You Cancer?

One of the benefits of living in our time is having access to the best medical care in history. Current medical imaging technology give physicians insight into their patients’ maladies, beyond what could have been imaginable a hundred years ago. But along with the benefits come risks.

Radiation Worries

Medical imaging, such as X-rays, mammograms and CT scans, are staple tools in diagnosing and helping patients. However, over the past decade or so there have been worries that the potential threat from the radiation exposure could be more harmful than previously thought.

The main concern is with techniques like CT scans and nuclear imaging – such as PET scans – which expose the patient to much higher doses of radiation than say a dental X-ray or biennial mammogram.

X-rays, CT scans and the like use ionising radiation that penetrates tissue and bone to give an image used for diagnoses. Ionising radiation is a known carcinogen that can also damage our DNA.

To put things into perspective, the average person gets about 3 millisieverts (mSv) of background radiation a year. In comparison, a chest X-ray gives you around 0.1 msV of radiation while a mammogram is about 0.4 mSv.

A CT scan of your chest, however, will give you a whopping 7 mSv in one go. That is the equivalent of 70 times that of a chest X-ray, or 2 ⅓ years of background radiation.

At the far end of the spectrum, during a PET/CT scan – which involves injecting the patient which radioactive material – you would receive 25 mSv, the same as seven years of background radiation.

The Risks of CT Scans

The CT scan has been revolutionary in terms of both eliminating the need for exploratory surgery and diagnosing a variety of medical problems, such as infections, tumours and heart disease, all of which have led to a boom in its usage.

In the US, CT scans increased from roughly three million in 1980 to more than 85 million by 2011. If this trend is congruent with the rest of the world it may present a potential time bomb.

A 2009 study by the National Cancer Institute in the US estimated that up to two percent of future cancer cases in the US could be related to CT scans taken in 2007. This matches a projected estimate by a team from the Centre for Radiological Research (CRR) at Columbia University in 2007.

The CRR team also noted studies that observed the effects of low-level radiation on both atomic bomb survivors from Japan and radiation workers in the nuclear industry.

These studies examined the at-risk groups who had between 5-150 mSv of radiation, or 40 mSv on average for bomb survivors and 20 mSv for radiation workers. Both groups had significantly increased chances of contracting cancer.

This indicates that the risk from CT scans is comparable as it only takes two or three CT scans to reach the same high levels of radiation.

Temper Caution

Although the risk of radiation from CT scans is a legitimate concern, it is important to note that generally speaking the risk is significant yet, put in perspective, still small.

According to the National Cancer Institute, you have roughly a 1 in 2000 chance of developing a fatal cancer from a CT scan. Compared to their statistic of a one in five lifetime risk of dying from cancer, the advantages seem to outweigh the disadvantages.

With that said, being aware of the risks allows you to voice any concerns with your doctor if you are recommended to undergo a CT scan. This is especially important if you undergo multiple CT scans within a short period of time.

The rewards of CT scans most likely outweigh the risks in most circumstances. However, knowledge is power. It still pays to be informed.



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