Radiation Exposure from Diagnostic Radiographs in Extremely Low Birth Weight Infants

Objective: We sought to examine radiation doses received by infants of less than 750 g birth weight from radiographs.

Methods: We examined the radiology records, including radiograph films, of all 25 surviving infants with birth weight less than 750 g admitted to our center during 1991. The standard method of neonatal radiation dose calculation was modified to consider the body size, postnatal growth, and extramedullary hematopoiesis of the extremely low birth weight infant. To determine overall radiation exposure, we calculated an effective dose equivalent, which is the sum of weighed organ dose equivalents.

Results: The infants had a mean of 31 radiographys performed, including 17 chest radiographs, 5 babygrams, and 9 abdominal radiographs. The majority of chest radiographs and babygrams were performed in the first month, whereas abdominal radiographs increased during the second month of life. Total-body radiation dose and total effective dose equivalent by the standard and modified methods, respectively, for single exposures ranged from 0.01 to 0.02 millisieverts (mSv) for a chest radiograph, from 0.02 to 0.04 mSv for a babygram, and from 0.02 to 0.03 mSv for an abdominal radiograph. Surface organs icluding the skin, breast, and thyroid received the largest radiation doses. The effective dose equivalent per infant for all radiographs was 0.72 mSv according to the modified method, compared to a total-body dose of 0.40 mSv using the standard method. However, infants with chronic lung disease or necrotizing enterocolitis received up to 1.5 mSv total-body dose, including 3.3 mSv to the breast, 2.5 mSv to the thyroid, and 2.3 mSv to the testes.

Conclusions: Radiation doses received by infants of less than 750 g birth weight are small in comparison with the range of doses that form the basis of risk estimates for cancer.