24. The Dangers of Ionizing Radiation: Which Radiologic Studies Should be Avoided, if Possible

If you find yourself (or your child) in an ER or doctor’s office, and the medical staff recommends imaging, keep this in mind: some forms of imaging are much safer than others. X-rays are high-energy studies utilizing ionizing radiation, meaning the energy is strong enough eject an electron from an atom. Luckily, the dose of ionizing radiation from a basic chest X-ray (CXR) or bone X-ray is quite minimal. When a CXR is performed, a patient receives a radiation dose equivalent to walking outside for about one week. CT scans, on the other hand, are high-radiation studies, and the exact dose depends upon which study is being performed. The radiation dose of a head CT scan, for example, is equivalent to about 200 CXRs, whereas the dose of an abdominal CT scan is closer to 600 CXRs! Why is this a problem? Exposure to ionizing radiation increases the risk of getting cancer later in life, in a dose-dependent fashion. Following the advent of frequent head CT scanning in the 1980s, brain tumor rates in this country markedly increased, and the relationship was unfortunately causal.

When it comes to radiation exposure, less is more, especially in children. Because their bodies (and brains) are still developing, children are more sensitive to radiation than adults. Since they’re going to live longer than their parents (hopefully), children have greater potential to acquire a significant cumulative dose of radiation over time. One head CT scan probably isn’t a big deal; but the total radiation dose adds up quickly if scans are repeated, either immediately or in the future. The pediatric pendulum has swung toward using studies that are radiation free, like ultrasound and MRI, as much as possible. If a doctor in an ER says that your child needs a CT scan, ask whether an ultrasound or MRI can be done instead. Usually the answer is yes, but you may have to put your foot down and demand that MRI. In many pediatric ERs, rapid MRI is fortunately replacing CT scans for brain imaging.

Along with abdominal and head CT scans, other pediatric imaging studies can increase the risk of developing cancer down the road. Below I’ve listed some common, problematic imaging studies:

  1. Neck CT scans are sometimes used to rule out deep tissue infections. However, these should be avoided because the thyroid gland, positioned in the center of the neck, is exquisitely sensitive to radiation.
  2. Voiding cystourethrograms, or VCUGs, are done to evaluate urinary reflux. The dose of radiation from a VCUG is roughly 3 millisieverts (mSv), or about 300 CXRs.
  3. An upper GI series is sometimes ordered to examine gut anatomy in children with intractable vomiting. While the study may be unavoidable, the dose of radiation is high at 6 mSv, equivalent to one abdominal CT scan or 600 CXRs. In general, the radiation dose incurred during any fluoroscopic study (which evaluates tissue movement in real time) can be quite high.