Why CT Scan Safety Is Back in the Spotlight: What a New Cancer-Risk Estimate Does and Doesn’t Mean

A new study has put CT scan safety back in the news, but the practical message for patients is not to panic. The paper, published in JAMA Internal Medicine, estimated the long-term cancer burden that could be linked to current CT use in the United States. It did not directly observe cancers caused by today’s scans, and it does not mean one medically needed CT scan is likely to cause cancer.

What it does mean is that radiation exposure from imaging still matters, especially when scans are repeated over time, when children are involved, or when the same medical question might be answered another way. For everyday readers, the takeaway is simple: needed imaging can be very important, sometimes lifesaving, but it is reasonable to ask informed questions.

What the new study found

The researchers used a modeling study, not a randomized trial or a direct follow-up of patients to see who later developed cancer. Using estimates based on CT use in 2023, radiation dose patterns, and established risk models, the authors projected that current CT imaging practices in the United States could be linked to a substantial number of future cancers over patients’ lifetimes.

That headline got attention for a reason. CT scans are common, and the study estimated about 93 million exams in roughly 62 million patients in a single year. When a test is used that often, even a small risk attached to each exam can matter at the population level. The authors also estimated that risk per scan was generally higher in children, while adults would account for most projected cases because adults get far more CT exams.

But that population-level estimate is also the study’s biggest limitation. It is a projection built from assumptions about radiation dose and future cancer risk, not proof that today’s scans will cause a measured wave of cancers in the real world. The model cannot tell any one person what will happen after a scan, and it should not be read as a reason to refuse urgent or medically necessary imaging.

What a CT scan actually is

CT stands for computed tomography. In plain language, it is a detailed imaging test that uses many x-ray images to create cross-sectional pictures of the inside of the body. Those pictures can help clinicians quickly see organs, blood vessels, bones, bleeding, swelling, infections, tumors, and other internal problems that may not show up as clearly on a regular x-ray.

According to the CDC, CT can be especially useful when doctors need speed and detail. That is why it is often used in emergencies, after injuries, during cancer workups, when internal bleeding is suspected, and when doctors need a closer look at infections, clots, or pain that is hard to explain.

In many situations, CT is ordered because it can answer an urgent question fast enough to change treatment right away. That benefit can easily outweigh the small radiation risk from a single exam.

Why radiation is part of the conversation

CT uses ionizing radiation, which is energetic enough to damage DNA. The FDA and CDC both note that medical imaging that uses radiation should be ordered thoughtfully, because added exposure may slightly increase lifetime cancer risk. That said, the key word is slightly for a single scan. Risk is not the same for every exam, and it can vary by body area, the scan settings, the patient’s age, sex, and overall clinical situation.

Concern grows more when exposure adds up over time. Someone with repeated scans for kidney stones, inflammatory bowel disease, cancer follow-up, or other chronic problems may have more reason to discuss whether each new scan is necessary and whether prior images can answer part of the question.

Children also deserve extra attention. Younger patients are generally more sensitive to radiation, and they have more years ahead in which a radiation-related cancer could theoretically develop. That does not mean children should not get CT scans. It means the scan should be clearly justified and the dose should be tailored to the child when possible.

Why this is about balance, not avoidance

Federal safety guidance has long focused on two ideas: make sure a scan is justified, and use the lowest radiation dose that still gets the information needed. In practice, that means avoiding unnecessary scans while not delaying care when imaging is important.

The American College of Radiology and other imaging groups made a similar point after the new paper came out: the study should not be mistaken for direct evidence that CT exams are causing a proven surge in cancer cases, and medically necessary scans still provide essential information.

That balance matters. A missed stroke, internal injury, appendicitis, pulmonary embolism, or cancer complication can cause immediate harm. For many of those problems, a CT scan may be the fastest or best tool available.

Who may want to ask more questions before a scan

Most patients do not need to fear a single ordered CT exam. Still, a few groups may benefit from a more detailed conversation:

Children and teens, because they are generally more sensitive to radiation.
People who get repeated scans, since cumulative exposure matters more than a one-time exam.
People who are pregnant or might be pregnant, because extra care is recommended when imaging could expose a developing fetus to radiation.
People with a history of contrast reactions, especially if IV contrast is planned.
People with kidney disease, diabetes, or both, because contrast dye may need extra review.

Questions to ask before an imaging appointment

If the situation is not an emergency, it is reasonable to ask a few practical questions:

What is this scan looking for, and how will the result change treatment?
Is this test needed now, or can we use recent images that already exist?
Could MRI or ultrasound answer the same question in this situation?
If CT is the best test, is the facility using dose-reduction techniques?
Will contrast dye be used?

If contrast is planned, tell the care team before the appointment if you have ever had a reaction to contrast dye. Most patients tolerate contrast without a serious problem, but prior reactions still matter. Also mention kidney disease, reduced kidney function, or diabetes medicines such as metformin. MedlinePlus notes that some patients taking metformin may be told to stop it temporarily before contrast imaging, and IV contrast can worsen kidney function in some people.

It is also important to say if you are pregnant or think you could be pregnant. The FDA advises patients to bring that up before x-ray-based imaging, including CT, so the team can decide whether the scan should proceed, be adjusted, or be replaced with another test when that makes sense.

None of that means MRI or ultrasound can always substitute for CT. Sometimes they can. Sometimes they cannot. The right test depends on the body part, the urgency, and the medical question.

What this means for readers

The new JAMA Internal Medicine paper is best understood as a reminder, not a warning to avoid care. CT scans use radiation, and repeated exposure can matter over time. But one medically necessary scan is not a reason to panic, and refusing urgent imaging on your own could be far more dangerous than the small long-term risk the study is trying to estimate.

The most useful response is informed decision-making. Ask why the scan is needed. Tell the team about pregnancy, kidney problems, past contrast reactions, and medicines such as metformin if contrast may be used. Ask whether previous images, a lower-dose approach, or a non-radiation test could work.

When the answer is that CT is the best test, patients should know that it remains one of medicine’s most valuable imaging tools.

Sources

This article is for general informational purposes only and is not medical advice. Research findings can be early, limited, or subject to change as new evidence emerges. For personal guidance, diagnosis, or treatment, consult a licensed clinician. For current outbreak or public health guidance, follow your local health department, the CDC, or another relevant public health authority.