A computed tomography (CT) scan uses a series of X-ray images taken from different angles to create detailed cross-sectional pictures of the body’s internal structures, including bone, soft tissue, and blood vessels. However, a CT scan delivers a substantially higher dose of ionizing radiation compared to a single X-ray, which is a source of concern for parents. The use of CT in pediatric medicine requires a careful balance: while it can be life-saving, the radiation exposure carries a small but real risk that must be managed.
Understanding the Radiation Risk to Children
Children are uniquely vulnerable to the effects of ionizing radiation for several biological and physical reasons. A child’s body contains more rapidly dividing cells than an adult’s, making them inherently more susceptible to DNA damage from radiation exposure. This increased sensitivity means the risk for a radiation-related cancer can be several times higher for a young child compared with an adult receiving an identical CT scan. Furthermore, a child has a much longer life expectancy, providing a greater window of time for any latent effects from radiation exposure to manifest later in life.
The risk is primarily associated with the cumulative dose of radiation received over time. Studies show a clear dose-response relationship between CT radiation exposure in childhood and the later development of specific cancers. For instance, a cumulative dose of 50 to 60 milligray (mGy) to the bone marrow or head has been linked to a threefold increase in the risk of leukemia and brain tumors, respectively. This dose could potentially be reached with as few as two to three head CT scans using older or unadjusted settings.
The physical difference in size also means that if adult settings are mistakenly used, the child receives a disproportionately higher effective radiation dose. Children’s organs are closer together, meaning the radiation beam may affect a wider array of sensitive tissues than in an adult.
When is a CT Scan Medically Necessary
The CT scan is essential in acute medical scenarios where rapid, accurate diagnosis is required. In cases of severe blunt trauma, a CT scan provides a quick evaluation of internal injuries, such as bleeding around the brain or damage to organs like the spleen, which can be life-threatening. The speed of the scan allows physicians to make immediate, time-sensitive decisions that can save a child’s life or prevent long-term disability.
In non-trauma cases, CT remains the gold standard for certain time-sensitive diagnoses when other imaging methods are inconclusive. For example, ultrasound is often the first choice for suspected acute appendicitis, but if results are unclear, a CT scan may be necessary to confirm the diagnosis. This confirmation helps prevent unnecessary surgery and ensures a ruptured appendix is not missed. A CT scan should only be ordered when the resulting information will directly influence the child’s treatment plan.
How Providers Reduce Radiation Exposure
The core principle guiding pediatric CT is ALARA, which stands for “As Low As Reasonably Achievable.” This principle directs medical professionals to limit radiation exposure as much as possible while maintaining the necessary image quality for diagnosis. One effective strategy is using weight-based or age-based protocols, which ensures the scanner settings are adjusted for the child’s smaller size instead of using a standard adult dose.
Technicians optimize settings by adjusting the tube voltage (kilovoltage peak or kVp) and the tube current (milliampere-seconds or mAs). Lowering these technical factors reduces the amount of radiation produced by the scanner. Newer CT scanners also employ sophisticated software called iterative reconstruction (IR), which uses complex algorithms to create diagnostic-quality images even when a lower radiation dose is used.
Strict attention is paid to targeted scanning, meaning the technologist only scans the specific area of the body required for the diagnosis, avoiding unnecessary radiation to adjacent sensitive organs. Some facilities accept slightly noisier images, as reducing the radiation dose often does not compromise the diagnostic outcome. These measures are part of a coordinated effort, promoted by campaigns like “Image Gently,” to standardize radiation reduction techniques across all facilities.
Safer Diagnostic Alternatives
Whenever possible, physicians use alternative imaging modalities that do not use ionizing radiation.
Ultrasound (US) employs high-frequency sound waves to create real-time images of soft tissues and internal organs. It is particularly effective and preferred for evaluating the appendix, kidneys, and ovaries in children, as it involves no radiation and is fast to perform.
Magnetic Resonance Imaging (MRI) uses powerful magnets and radio waves to generate highly detailed images of the brain, spine, and soft tissues. While MRI provides superior detail for certain conditions, it has limitations: the scan is much slower than a CT, often taking up to an hour. This slow speed may require sedation for young children to remain perfectly still. While these alternatives are used as a first line, their diagnostic capabilities cannot fully replace CT in every emergency or critical situation.