Hospitals rely on CT scans every day, yet a new analysis suggests today’s habits could quietly seed tens of thousands of future cancers.
Researchers are raising fresh questions about how often we should be scanned, and at what radiation doses, just as CT use keeps climbing in hospitals and emergency rooms across the United States.
What a new study is warning about
A study in the journal JAMA Internal Medicine looked at how many CT scans Americans undergo and what that might mean decades from now. The team focused on 2023, a single recent year.
They estimated that around 93 million CT scans were carried out on about 62 million people in the US. From there, they modelled how radiation from those scans could influence lifetime cancer risk.
The authors project that current CT use could lead to roughly 103,000 additional cancers in the future if scanning habits and doses stay the same.
That number is not a count of cancers already seen. It is a forecast based on how radiation is known to affect tissue, multiplied across millions of patients.
If nothing changes, the study suggests CT-related cancers could eventually account for close to 5% of all newly diagnosed cancers each year in the US. That is not a majority, but it is too large to ignore in a health system already struggling with cancer care costs and staffing.
CT scans: a powerful tool with a hidden cost
CT, or computed tomography, uses X‑rays to create detailed cross‑section images of the body. Doctors use it to look at:
- organs such as the liver, lungs and kidneys
- bones and joints after injuries
- blood vessels, to spot clots or aneurysms
- soft tissues, to detect tumours, infections or internal bleeding
Compared with a standard X‑ray, a CT scan usually delivers far clearer images. That clarity can be the difference between a missed diagnosis and a life saved, especially in strokes, major trauma or suspected internal bleeding.
The trade‑off is dose. A single CT scan can expose a patient to dozens or even hundreds of times more radiation than a plain chest X‑ray. The body can repair some damage, but not all. Each exposure adds a tiny extra risk that cells will mutate and turn cancerous later on.
➡️ The Norfolk home of the grandmother of Diana, Princess of Wales, has come to the market
➡️ Uninhabitable by 2100″: the countries condemned by extreme rainfall
➡️ The difference between brown and white eggs finally explained by science
➡️ As It Slowly Drifts Away From Earth, The Moon Is Changing The Length Of Our Days And Our Tides
➡️ The proof that destroying forests changes the climate: a deforested zone warmed by 4°C
Children and teenagers carry a higher risk
One of the starkest findings from the new work is how uneven the risk is across ages. Children and teenagers appear far more vulnerable to CT-related cancers than adults.
That is for several reasons. Young tissue divides more quickly, so DNA damage is more likely to be copied and amplified. Children also have many decades of life ahead of them, which gives any damaged cells more time to grow into a tumour.
The study suggests radiation‑induced cancers from CT scans will be more frequent among children and adolescents than in adults, scan for scan.
In adults, CT scans of the abdomen, pelvis and chest carry the largest projected risk. In children, scans of the head are particularly concerning. The developing brain, thyroid and nearby tissues are all sensitive to X‑rays.
Cancers thought to be most affected by CT radiation include those of the lung, colon, blood (such as leukaemia), bladder, breast and thyroid.
Radiologists push back on fears
Radiology groups stress that these new figures are estimates, not direct counts of patients harmed by a specific scan. The American College of Radiology reacted quickly, arguing that no clear causal link has been definitively shown between medical CT scans and cancer in humans at the doses currently used.
They emphasise benefits that are easy to see in everyday practice. CT can catch a stroke in time for clot‑busting drugs, pick up a dangerous blood clot in the lungs, or detect early cancers that might be completely invisible on a standard X‑ray.
For many conditions, radiologists argue that the life‑saving potential of CT scans outweighs the relatively small theoretical cancer risk when the scan is medically justified.
In other words, skipping a vital CT could cost a life now, while the extra cancer risk may be one or two cases per several thousand people scanned.
“Less, but better”: what changing practice could look like
Where most experts agree is on the need to reduce unnecessary scans and to fine‑tune the radiation dose in those that are truly needed.
Cutting down on unnecessary CT scans
Doctors and hospitals can limit avoidable radiation without losing diagnostic power. That can include:
- using ultrasound or MRI when they provide similar answers without radiation
- following stricter guidelines on when to order CT in emergency departments
- avoiding repeat scans when previous images are still usable
- sharing images between hospitals instead of rescanning patients who move
Several countries already track CT use and give feedback to hospitals that scan more than average for common conditions. The aim is not to punish doctors, but to question whether all those scans truly change care.
Lowering the dose, scan by scan
CT machines can be adjusted. Radiologists can often reduce the dose while keeping image quality high enough for a safe diagnosis, especially in smaller or thinner patients and in children.
| Strategy | Effect on patients |
|---|---|
| Automated dose modulation | Machine tailors X‑ray output to body size, lowering exposure |
| Pediatric protocols | Special child‑sized settings cut radiation for younger patients |
| Scan only the needed area | Reduces exposure to organs outside the region of interest |
| Limit multi‑phase scans | Fewer passes means fewer cumulative X‑rays |
Many hospitals already use these approaches, though not always consistently. The study’s authors argue that wider adoption could sharply reduce projected cancers without losing the lifesaving upside of CT.
What patients and parents can do
Individuals have limited control over the technical settings of a CT scanner. Still, there are questions worth asking before you lie down on the table.
- Is this scan truly needed? Ask what the doctor hopes to find and whether another test could work.
- Has this been scanned before? If you had a CT at another hospital, ask if those images can be obtained.
- Are there child‑specific settings? For children, check that the imaging unit routinely adjusts dose for age and size.
- What happens if we wait? In non‑emergencies, sometimes monitoring symptoms first is safe.
These discussions will not eliminate CT scans, and they should not delay urgent care. They do help ensure each exposure has a clear purpose.
Understanding the numbers behind the fear
Radiation risk often sounds abstract. To make it more concrete, researchers use something called “effective dose,” usually measured in millisieverts (mSv). A chest X‑ray might be about 0.1 mSv. A typical CT of the abdomen can easily reach 10 mSv or more.
Health agencies estimate that for every 10,000 people exposed to 10 mSv, a small number will eventually develop a radiation‑related cancer. That might be on the order of one extra case, though estimates vary. Against a background rate where thousands already develop cancer naturally, one extra case is hard to see in real‑world data. That is why many of these studies rely on modelling rather than direct observation.
Now scale that tiny individual risk across tens of millions of scans, and the totals start to look troubling. The same logic applies to other everyday exposures, from air pollution to chemicals at work: low risk per person, but potentially large effects at the population level.
Key terms that shape the debate
Several medical words come up again and again in discussions about CT and cancer risk:
- Abdomen: the part of the body between the chest and the hips, housing organs like the stomach, liver and intestines.
- Colon: the long part of the large intestine, where colon cancer can develop.
- Bladder: the muscular sac in the pelvis that stores urine.
- Thyroid: a small gland in the neck that controls metabolism and is sensitive to radiation.
These organs are often in the direct path of the X‑ray beam during CT scans. That is why they show up so often in risk estimates.
Looking ahead: balancing early diagnosis and long‑term safety
The same imaging technology that helps spot lung cancer early can, in theory, play a tiny role in creating cancer later on. This tension sits at the heart of modern medicine: more testing can save lives, but more testing also carries its own hazards.
Some researchers are now modelling different futures. One scenario keeps CT use where it is but halves the average radiation dose per scan. Another trims back low‑value scans in emergency departments, especially for young, otherwise healthy patients with minor injuries. In those simulations, the projected number of future cancers drops dramatically, while urgent diagnoses remain intact.
For now, the message is not to fear every CT scan, but to treat each one as a medical intervention with both benefits and risks. When a scan guides surgery, prevents a stroke or rules out a life‑threatening injury, the balance is clear. The real question raised by the new estimate of 103,000 extra cancers is how many scans do not meet that bar, and how quickly health systems are willing to change that.