To Scan or Not to Scan?

The risks and benefits of CT scans — and what you can do to protect your children

Anyone who has brought a child with severe abdominal pain or a head injury to the emergency room is likely familiar with the use of CT scans, which can be used to quickly diagnose a problem even in the youngest, squirmiest of children. Computed tomography (CT), formerly known as ‘CAT’ and now simply ‘CT’, has revolutionized diagnostic medicine, and its use has increased exponentially in children since its debut in the 1970’s. But as use of CT has increased, so has concern for cancer risk associated with the corresponding radiation exposure.

How safe are CT scans in children, and what should we do to best protect our children’s health?

William Middlesworth, MD, Pediatric Surgeon at Morgan Stanley Children’s Hospital at NewYork-Presbyterian, helps us to understand the risks posed by radiation exposure from medical imaging. Children are especially vulnerable, in part because cancer risk is related to the cumulative dose of radiation over one’s lifetime.

What is ionizing radiation?

There are various sources of ionizing radiation, both naturally-occurring and man-made. Natural sources, which account for 85% of our exposure, include the sun, lightning, cosmic radiation from outer space, and radon gas, among others. The remaining 15% comes from man-made sources, the major source being medical testing such as nuclear medicine and CT scans. While CT scans provide invaluable, sometimes lifesaving imaging of the abdomen and other parts of the body, they involve significantly higher doses of radiation than X-rays.

How does radiation damage our health?

The dangers associated with radiation vary depending on the amount of the radiation (or radiation dose), the length of exposure, and the part of the body exposed, because some parts of the body are more sensitive than others.

If exposure is very high in a particular incident (think Chernobyl), the radiation directly harms and kills cells rapidly, causing radiation sickness that may be fatal. If the exposure dose is low, such as in exposure to natural sources or medical testing, it can cause damage to our DNA and can cause formation of free radicals, molecules that are highly reactive and are thought to cause many health conditions including cancer. While the body naturally repairs most damage of this type, some of these effects are less easily repaired. If the body cannot repair DNA damage, it can continue to progress over many years, ultimately leading to cancer.¹

Children are more sensitive than adults to the effects of radiation, and studies show that childhood CT scans increase the lifetime risk of brain tumors, leukemia, thyroid cancer, colon cancer, and others.² The younger the age of the child, the greater the sensitivity to the effects of ionizing radiation.

A study published by researchers at NYP/Columbia in 2000 found that for every 600,000 abdominal and head CT examinations performed in children under 15 years of age, approximately 500 of these patients might ultimately die from cancer attributable to CT radiation they received as a child.³ A 2013 study found that nationally, approximately 4 million CT scans in children are projected to cause 4870 future cancers.⁴ Many other studies corroborate the association between childhood CT scans and increased risk of cancer later in life. ^{5 6}

What is a parent to do?

In short, the best approach to testing involves a careful evaluation of benefit versus risk, and when choosing to proceed with CT scanning, using the lowest dose possible. Parents can ask several questions to help ensure their children’s doctors are doing everything they can to achieve this.

Does the benefit outweigh the risk? Parents should confirm that the benefits of undergoing the test are important enough to warrant testing despite potential risks in the future. Doctors should be able to explain why the risk of missing an important diagnosis may be greater than risk of a late cancer, and why alternative treatment options would not be as good.

Ask if the radiologists are following ALARA recommendations.The Society for Pediatric Radiology issued guidelines for dose-reducing strategies called “As Low As Reasonably Achievable,” commonly called ALARA, in 2001. These guidelines aim to minimize radiation risk by adjusting the radiation emitted in a test according to the child’s weight. While this may reduce the resolution of an imaging study, the lower resolution image may still provide sufficient information for doctors to make their diagnoses and treatment decisions. As Dr. Middlesworth explains, “We want to avoid over-dosage that does not provide helpful information.”

With increased public awareness of radiation risk, more hospitals have adopted the ALARA guidelines, and the use of CT scanning in children has been declining in the past few years. ⁷

Ask if a diagnostic test that does not involve radiation exposure may be substituted for one that does. In some cases, alternate methods of testing such as ultrasound (US) or magnetic resonance imaging (MRI) may be used instead of CT scanning. In cases of suspended acute appendicitis, for example, it may be feasible to use US (which is radiation-free) as an initial test, followed by selective use of MRI where needed. This approach has been shown to be as effective as CT, according to a study published by Dr. Middlesworth, Dr. Gudrun Aspelund, and colleagues at NYP/Columbia in 2014.⁸ Dr. Middlesworth notes that the accuracy of ultrasound can vary, depending on the examiner and how he or she conducts the test. In some cases ultrasound may be prone to error, or the organs may not be viewable; for example, viewing the appendix in a child who is obese may not be possible. However, parents should feel free to ask whether it would be possible to use ultrasound instead of CT, and avoid CT for their children.

Finally, a last but important way to reduce CT scanning is simply to make sure that tests are not repeated due to failure of medical personnel to communicate with one another. Unfortunately, it is a common occurrence that test results may not be communicated from one practitioner or institution to another, leading to unnecessary duplication of testing in more than 20 million adults and one million children per year.