Written by Amen Dilawar

A major new study in the New England Journal of Medicine is raising concern about how often children are exposed to medical imaging that uses radiation. According to the study, about 1 in 10 childhood blood cancers, or around 3,000 cases, may be linked to radiation from medical imaging. It found that imaging tests, such as X-rays, CT scans, and fluoroscopic procedures, may contribute to a higher risk of blood cancers, necessitating a change in the standard for using this technology on children. 

The study, funded by the National Cancer Institute and other organizations, was led by Dr. Rebecca Smith-Bindman of the University of California, San Francisco along with Susan Alber, Marilyn Kwan, Priscila Pequeno, Wesley Bolch, Erin Bowles, Robert Greenlee, and Diana Miglioretti. The study comprised 3,724,623 children across six major health care systems in the United States and in Ontario, Canada. These children were born between 1996 and 2016 and were tracked until they were diagnosed with a hematologic (blood-related) cancer or a benign tumor (nonspreadable to other parts of the body), until they died, until they lost health coverage, until they turned twenty one, or until the end of 2017. The research examined how much radiation reached the active bone marrow and how that exposure related to later cancer diagnoses. 

The researchers measured radiation exposure using milligray units. A milligray is the amount of energy absorbed by the body. A single CT scan of the head can expose a child to about 13.7 milligray of radiation, and even low doses (1-5 mGy and 15-20 mGy) were associated with increased risk compared to no exposure. Children who received at least one milligray of radiation from imaging had an average total exposure of fourteen milligray across all their scans. Children who developed hematologic cancer had an average exposure of about twenty four milligray. 

The study recorded more than thirty five million person years of follow up. Person years represent the total amount of time the children were observed. This number comes from adding together the years each child spent in the study. The average follow up time was a little more than ten years per child. During this period, 2,961 hematologic cancers appeared in the group, with lymphoid cancers, which are cancers of the white blood cells of our immune systems, making up about 79% of cases. These cancers affect the white blood cells in the lymphatic system, including the lymph nodes and other tissues that protect the body from infection. Acute leukemia and other myeloid cancers made up about fifteen percent. These cancers start in the bone marrow, which produces new blood cells. Histiocytic and dendritic cell cancers made up a smaller number of cases. These cancers involve rare immune cells that help the body respond to foreign substances. 

The study found that children with higher cumulative radiation to the bone marrow had a higher risk of cancer. Even low exposure mattered. Children who received between one and five milligray had a relative cancer risk of 1.41 compared to children with no exposure. Children who received between fifteen and  twenty milligray had a relative risk of 1.82 compared to children who had no measurable exposure. Children who received between fifty and one hundred milligray had a relative risk of 3.59 compared to children with zero exposure. The excess relative risk for every one hundred milligray was 2.54. The relative risk for thirty milligray compared to no exposure was 1.76. The researchers estimated that by age twenty one, children who received at least thirty milligray had an excess cumulative incidence of 25.6 hematologic cancers per ten thousand children compared to children who received no radiation exposure. These findings support the idea that cancer risk increases steadily as radiation exposure increases. 

In general, children face higher risk from radiation because their bodies are still developing. Their cells divide more quickly than adult cells. That rapid growth makes them more likely to experience long-term damage from radiation such as DNA mutations that could lead to cancer, disruptions in normal blood cell development, and errors in how immune cells form and function. Children also have many years of life ahead, so the effects of that exposure can appear decades later. 

One of the key findings of the study is that low levels of radiation can still increase cancer risk. A child may receive only one or two CT scans, yet that exposure can matter. Smaller tests such as standard X-rays also add to the overall radiation dose. These findings depict that routine imaging is not harmless and should be used with caution. 

Many physicians rely on imaging early in the diagnostic process. It has become a standard part of care for injuries, infections, stomach pain, and many other conditions. This study raises the concern that imaging may sometimes be ordered without careful consideration. Dr. Smith-Bindman said that every test that uses radiation should have a clear purpose. Physicians should avoid ordering a scan simply because it is quick or widely available. 

In some cases, safer options already exist. Ultrasound can often diagnose appendicitis in younger children. It does not expose the child to radiation. Many hospitals still move older children straight to a CT scan, even though the ultrasound method also works in these cases. Dr. Smith-Bindman said that clearer guidelines are needed. These guidelines would help physicians choose the safest test and help reduce unnecessary radiation. 

Parents play an imperative role as well. They should not refuse imaging when a child is seriously injured or very ill. In emergencies, scans are essential. Outside of those situations, parents can ask simple and respectful questions. They can ask if the test is necessary. They can ask if the timing is urgent. They can ask if the clinic uses pediatric settings to reduce the dose. They can also ask if an ultrasound or MRI can answer the same question. These conversations can help both the physician and the family think carefully before committing to a radiation-based test. They also support shared decisions about a child’s health. 

This  study is not meant to discourage the use of imaging in general. It is meant to encourage thoughtful use. Medical imaging saves lives. It can detect serious problems quickly. It can guide treatment and prevent complications. The goal is to use these tools responsibly and at the lowest dose possible.

The research provides strong evidence that cumulative radiation exposure matters. It also shows that many imaging decisions involve judgment. As more hospitals and clinics review these findings, there may be a shift toward safer alternatives, clearer protocols, and better communication with families. 

Dr. Smith-Bindman hopes the study will lead to a culture of careful decision-making. She believes that simple steps can protect children while still giving them the medical care they need.

Edited by Alexandra Zhikharev