If you have ever watched a medical drama like Grey’s Anatomy, you know that computed tomography (CT) scans are very common. They are used to find tumors, locate blood clots, diagnose many types of cancers, get detailed images of broken bones, and much more.

Each year, millions of people get a CT scan, and the results of these scans have saved untold millions of lives over the years. According to a study published in JAMA Internal Medicine, however, the scans have also likely caused cancer in many patients.

CT scans work using X-rays just like traditional X-ray machines, except that the X-ray itself is spun around the patient to take much more detailed images. This means greater exposure to the ionized radiation, which can cause cancer.

The study was led by Dr. Rebecca Smith-Bindman of the University of California, San Francisco. It is estimated that more than 61.5 million people got at least one CT scan in 2023. Based on the model used in the study, it is projected that 103,000 of these people will develop cancer because of the scans.

That accounts for about 5% of the two million new cancer cases each year. This means that CT scans have a very similar risk level to things like heavy drinking and obesity. The cancers most commonly caused by a CT scan include colon, lung, leukemia, bladder, and breast cancer.

CT scans of the abdomen seem to pose a greater risk than other parts of the body.

Of course, medical professionals have always known that X-rays can cause cancer, and since CT scans use the same technology, they know that it, too can be a problem.

It is hoped that this study will be a reminder to doctors of the very real dangers associated with CT scans. In many cases, the benefits will clearly outweigh the risks since these scans can provide extremely valuable information that can help to save the life of a patient. When possible, however, other scans like ultrasounds should be used since they don’t pose the same threats.

Lynda Johnson is the Professional Officer for Clinical Imaging and Radiation Protection at the Society and College of Radiographers. She gave a statement to Science Media Centre, saying:

“Accurate communication around the benefits and risks of CT is essential to protect the public from harm. Focusing on risk alone is not helpful and, in some cases, might prevent a person from attending a scan that could provide early diagnosis of cancer.”

This makes a good point. Patients who read this study may be hesitant to get a CT scan, even when it is the best option for their situation. It is important to work closely with your doctors and other medical professionals to determine what treatments and what tests will provide the best results.

There is no argument that CT scans are a powerful tool in the arsenal of doctors, but they should only be used when appropriate.

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