The risks from the dose of radiation used in computed tomography (CT) scans to collect images of the inside of a patient is very low. While a single CT scan can expose patients to a significant amount of radiation when compared with techniques like conventional x-ray imaging, the increased chances of developing cancer as a result are low overall because it is a one-time event. If patients have repeat scans, they can become a cause for concern. There are some steps doctors can take to limit the risk of a CT radiation dose.
In CT scanning, a series of images is taken of the area of interest to generate a detailed image of the inside of the patient's body. A typical CT can expose a patient to between 1 and 10 millisieverts (mSv) of radiation, although in some patients the exposure may be higher because of the type of scan. For a patient who needs a CT of the abdomen and pelvis where the doctor wants a set of scans with and without a contrast agent, for example, the patient's radiation exposure from the scan amounts to about 10 years' worth of average background radiation.
Exposure to radiation can elevate the chances of developing cancer in the future, and there is a low increased cancer risk in patients who receive CT scans. A single diagnostic scan carries a relatively minimal cause for concern, especially when weighed against the benefits of the scan. The CT radiation dose can become an issue if a patient needs multiple scans as part of an ongoing series of diagnostic tests and evaluations. It is also a problem when patients receive unnecessary tests.
To lower the CT radiation dose, doctors can use filtering and other techniques to limit the amount of radiation. They must also carefully consider every patient case to decide if this type of imaging is really necessary or appropriate. With pediatric patients, who are more sensitive to radiation, the doctor may consider the increased risks and concerns about lifetime radiation exposure. A patient who needs numerous scans as a child may need more as an adult, because there may be a complex medical problem that would require follow-up. Over time, the patient's cumulative CT radiation dose could get quite high.
For pregnant patients, there are also special concerns with the CT radiation dose. As a general rule, care providers try to limit the use of radiologically active materials around pregnant patients. This protects the developing fetus and can prevent the onset of health problems later in life. When a pregnant patient absolutely needs a CT, the doctor may use more shielding, filters, and other options to keep the exposure minimized.
Beyond the CT radiation risk, there are also some other concerns with medical imaging studies of this nature. If a test has ambiguous results, the patient may need more testing, including invasive procedures, to clear up the results, and this can be expensive and traumatic. Furthermore, some patients have allergic reactions to the tracer materials used in medical imaging studies.