Radiation Exposure in 212 Very Low and Extremely Low Birth Weight Infants

Objective: We determined the frequency and estimated effective radiation dose (E) from conventional diagnostic radiographs for infants who had birth weight of <or=1500 g (very low birth weight [VLBW] infants) and were treated in a NICU.

Methods: Entrance skin doses were experimentally measured for all standard weight-dependent exposure settings. For each radiograph in the radiologic file, the exposed area on the film was measured manually. Together with clinical data obtained from the Vermont Oxford Network, medical charts, and radiologic files, we estimated E. E values per radiograph and per child were compared with recommended reference values and annual natural background radiation (NBR). We used reference data to estimate the risk for radiation-induced cancers.

Results: Of 212 VLBW infants, 194 required at least 1 conventional radiograph. Measured entrance skin dose varied between 11.8 and 15.0 microGy. Calculated E received was 16 microsievert (microSv; median) per radiograph and 71.5 microSv (median) per infant for the whole stay. Infants with birth weight <or=750 g, length of stay >or=16 weeks, congenital malformations, or oxygen dependence for >or=36 weeks were at risk for high numbers of radiographs and high radiation dose. Compared with the annual NBR, the median of 4 radiographs per infant contributes 12 days of NBR. We estimated that only 1 of 60000 NICU-treated VLBW infants will develop a fatal malignancy up to 15 years of age.

Conclusions: We found that NICU-treated VLBW infants had low radiation exposure compared with the annual NBR.