Radiation dose to neonates on a Special Care Baby Unit.

Neonates on a Special Care Baby Unit often require radiography to monitor the progress of their treatment and as a result can have a large number of radiographs taken during their stay in hospital. The skin entrance dose was estimated from a knowledge of the technique factors, X-ray tube output and backscatter factors. Normalized organ dose data were employed to estimate the radiation dose to a number of critical organs. A number of methods of reducing the radiation dose to neonates were investigated. Initially, this involved changing the radiographic technique factors and introducing a lead rubber adjustable collimator, placed on top of the incubator, in addition to the light beam diaphragms on the X-ray tube. It was deduced from the results of calculations that these modifications to the radiographic examination technique had reduced the average entrance dose per radiograph from 92 mu Gy to 58 mu Gy, a reduction of 37%. Later, a rare-earth film-screen combination was introduced to replace the existing fast calcium tungstate screens. This enabled the average entrance dose per radiograph to be reduced to 39 mu Gy, a further reduction of 33%. The mean radiation dose to a neonate is mainly determined by the number of radiographs taken and this is dependent on the clinical symptoms.