Reference dose levels for patients undergoing common diagnostic X-ray examinations in Irish hospitals

Wide variations in patient dose for the same type of X-ray examination have been evident from various international dose surveys. Reference dose level s provide a framework to reduce this variability and aid in the optimizatio n of radiation protection. The aim of this study was to establish, for the first time, a baseline for national reference dose levels in Ireland for fo ur of the most common X-ray examinations: chest, abdomen, pelvis and lumbar spine. Measurements of entrance surface dose using thermoluminescent dosem eters (TLDs) for these four X-ray examinations were performed on 10 patient s in each of 16 randomly selected hospitals. This represented 42% of Irish hospitals applicable to this study. Results have shown wide variation of me an hospital doses, from a factor of 3 for an anteroposterior lumbar spine t o a factor of 23 for the chest X-ray. The difference between maximum and mi nimum individual patient dose values varied up to a factor of 75. Reasons f or these dose variations were complex but, in general, low tube potential, high mAs and low filtration were associated with high-dose hospitals. This study also demonstrated lower reference dose levels of up to 40% when compa red with those established by the UK and the Commission of the European Com munities for four out of six projections. Only the chest X-ray exhibited a similar reference level to those established elsewhere. This emphasizes the importance of each country establishing its own reference dose levels that are appropriate to their own radiographic techniques and practices in orde r to optimize patient protection.