My 6 week old baby just had a skull X-Ray that consisted of 5 X-Ray images. Her radiation dose was estimated to be 0.4 mSv. I have been worried about her exposure to this radiation and was wondering if you could help me understand what risk this puts her at for future complications or cancer being that her age is so young? Thank you so much for your help.
The risks associated with high energy radiation (such as x-rays and gamma rays) have been studied for many years. It is widely recognized that large amounts ("high doses") of such "ionizing" radiation can be harmful. However, there is not widespread agreement about the risks associated with smaller amounts of this radiation, such as the amounts used for medical imaging. The biological effects from low doses of ionizing radiation (x-rays and gamma rays) are actually still something of a mystery. There are theoretical models that predict that low doses (amounts just above the "background" level that we are surrounded by while living on earth) can be the cause of cancers that appear many years in the future. There are other models that support the notion that low levels of ionizing radiation (less than ~100 mSv) are harmless. Both of these ideas have supporters in the scientific community. But due to the fact that cancer is a common disease (42% of individuals are diagnosed with cancer during their lifetime), it is impossible to say that an individual cancer diagnosis was caused by radiation, as opposed to a "natural" cancer or from some other cause. For the same reason, the uncertainty that is inherent in biostatistics suggests that we will never know with confidence whether low levels (less than 100 mSv) of radiation exposure increases one's lifetime cancer risk, or has no effect at all. You can think of this like the risk of getting lung cancer from smoking 1 cigarette, or the risk of dying in a fatal car crash during 1 road trip. In these examples, the risk is very close to zero or may actually be zero.
With respect to your question about 5 x-ray images of the head of a 6-week-old baby, we can say that the total radiation dose from these 5 x-rays is indeed low, only a fraction of 1 mSv. The theoretical risk associated with this exposure is so small that it cannot be calculated. In addition, we know that the body repairs DNA damage caused by ionizing radiation. Small doses of radiation are easily repaired, while high doses can overwhelm the repair system, leading to lasting damage and subsequently more long-term cancer risk. We know this from studies of people who received very high doses of radiation.
The x-rays that your child experienced produced images that undoubtedly aided in your child's care. Such images are invaluable in improving human health. All patients (or their proxies) must weigh the benefits of medical technology against the costs and risks, and one of those risks is the small theoretical risk from ionizing radiation, which is possibly even zero. The Hippocratic oath requires medical professionals to justify tests and procedures by ensuring that the benefits exceed the risks. Through open communication between patients and their doctors, patients can feel confident that their medical tests (such as diagnostic imaging tests with x-rays and gamma rays) are justified and the benefits exceed the very small risks.