AN INVESTIGATION INTO TECHNIQUES FOR REDUCING DOSES FROM NEONATAL RADIOGRAPHIC EXAMINATIONS

A survey of radiation doses received by infants having radiography in a neo-natal unit was undertaken at Aberdeen Maternity Hospital Options for dose reduction recommended by the CEC Lake Starnberg Group were investigated. Techniques were implemented for clinical evaluation after assessments of image quality with test objects and phantoms. Clinical image quality of radiographs was evaluated by paediatric radiologists using CEC criteria Results revealed a clear relationship between entrance dose and patient weight, indicating that reference doses for infants could be linked to weight. At the start of the study the mean entrance dose for chest anteroposterior (AP) radiographs was 65 mu Gy and the dose-area product 12.3 mGy cm(2) for a system with 2.5 mm aluminium filtration using 50 kVp X-rays with a 200 speed class film/screen system. A 400 speed dass film/screen combination was investigated but not evaluated clinically, because the image quality was not considered acceptable. Addition of 0.1 mm copper to the filtration of the X-ray tube reduced entrance doses by 50%, but the technique was not adopted, because of a poorer image quality with only 72% of features in clinical images being reproduced to an acceptable standard, compared with 87% with the original system. Use of faster processing chemicals, an increase in filtration to 3.5 mm aluminium and a tube potential of 60 kVp resulted in a 40% reduction in mean entrance dose to 37 mu Gy with satisfactory clinical image quality.