A study of the relationship between patient dose and size in paediatric radiology.

Entrance doses and dose-area products have been measured for paediatric X-ray examinations in a dedicated paediatric department. Dose-area products for barium meal and micturating cystourethrogram examinations involving fluoroscopy were substantially less than results from other studies. A number of factors contribute to this, including a high gain image intensifier used without a grid, shorter screening times, smaller numbers of films, exclusive use of a 100 mm camera and careful collimation of the X-ray field. Entrance air kerma has been measured for pelvis, abdomen, chest and skull radiographs. The relationship between dosimetric quantities and an equivalent patient diameter derived from data on patient height and weight has been studied. The results show a linear relationship between the logarithm of entrance air kerma and equivalent patient diameter for radiographic examinations performed on a single X-ray unit. Application of exponential correction factors could allow entrance doses for radiographs of children of different ages to be compared with appropriate reference doses.