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 t he radiology records, including radiograph films, of all 25 surviving infants with birth weight less than 750 g admitted to our tenter durin g 1991. The standard method of neonatal radiation dose calculation was modified to consider the body size, postnatal growth, and extramedull ary hematopoiesis of the extremely low birth weight infant. To determi ne overall radiation exposure, we calculated an effective dose equival ent, which is the sum of weighted organ dose equivalents. Results. The infants had a mean of 31 radiographs performed, including 17 chest ra diographs, 5 babygrams, and 9 abdominal radiographs. The majority of c hest radiographs and babygrams were performed in the first month, wher eas abdominal radiographs increased during the second month of life. T otal-body radiation dose and total effective dose equivalent by the st andard 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 0.01 to 0.03 mSv for an abdomi nal radiograph. Surface organs including the skin, breast, and thyroid received the largest radiation doses. The effective dose equivalent p er infant for all radiographs was 0.72 mSv according to the modified m ethod, compared with a total body dose of 0.40 mSv using the standard method. However, infants with chronic lung disease or necrotizing ente rocolitis received up to 1.5 mSv total-body dose, including 3.3 mSv to the breast, 2.4 mSv to the thyroid, and 2.3 mSv to the testes. Conclu sions. Radiation doses received by infants of less than 750 g birth we ight are small in comparison with the range of doses that form the bas is of risk estimates for cancer.