Radiation protection in pediatric radiology

Abstract

Background: The German Federal Law on Radiation Control contains no special provisions for X-ray studies in children and adolescents, even though exposure to ionizing radiation must be kept especially low in young persons, because their tissues are highly radiosensitive. Children, who have many years left to live, are more likely than adults to develop radiation-induced cancer; also, as future parents, they are at risk for passing on radiation-induced genetic defects to the next generation. Whenever possible, radiological studies on children and adolescents should be of a type that does not involve ionizing radiation, such as ultrasonography or magnetic resonance imaging. Pediatric conventional X-rays and computerized tomography (CT) require special examining techniques and protocols that are adapted to the patient's age and to the indication for the study.

Methods: We selectively review the literature on pediatric dose reduction and discuss our own investigations on the subject as well.

Results: The essential technical prerequisites for lowering the dose of ionizing radiation in conventional X-ray studies include the proper setting of tube voltage, the use of tube filters, suitable patient positioning and fixation, variable use of a scattered-radiation grid, and a modern storage-plate system. In CT studies, the use of age- and indication-adapted protocols can lower radiation exposure by as much as 95%.

Conclusion: There are now many ways to lower the exposure of children and adolescents to ionizing radiation without sacrificing diagnostic reliability. The main factors in lowering exposure are proper attention to clinical indications, the use of special X-ray protocols, the use of alternative imaging studies without ionizing radiation wherever possible, and the expertise of the examiner.

Figure 1

Estimated organ doses and lifetime cancer risks from typical single CT scans of the head and the abdomen. Panels A and B show estimated typical radiation doses for selected organs from a single typical CT scan of the head or the abdomen. As expected, the brain receives the largest dose during CT of the head and the digestive organs receive the largest dose during CT of the abdomen. These doses depend on a variety of factors, including the number of scans (data shown are for a single scan) and the milliamp-seconds (mAs) setting. The data shown here refer to the median mAs settings reported in the 2000 NEXT survey of CT use. For a given mAs setting, pediatric doses are much larger than adult doses, because a child’s thinner torso provides less shielding of organs from the radiation exposure. The mAs setting can be reduced for children (but is often not reduced); a reduction in the mAs setting proportionately reduces the dose and the risk. The methods used to obtain these dose estimates have been described elsewhere,20 but software that estimates organ doses for specific ages and CT settings is now generally available. Panels C and D show the corresponding estimated lifetime percent risk of death from cancer that is attributable to the radiation from a single CT scan; the risks (both for selected individual organs and overall) have been averaged for male and female patients. The methods used to obtain these risk estimates have been described elsewhere. The risks are highly dependent on age because both the doses (Panels A and B) and the risks per unit dose are age-dependent. Even though doses are higher for head scans, the risks are higher for abdominal scans because the digestive organs are more sensitive than the brain to radiation-induced cancer. (N Engl J Med 357; 22:2277–84)

Figure 2

Examples of radiation protection in hip X-rays

Figure 3

Radiation protection in X-rays

Figure 4

Radiation protection in computed tomography