EuroSafe Imaging 2020
Not applicable, Retrospective, Dosimetric comparison, Radiation safety, Physics, Dosimetry, CT, Radioprotection / Radiation dose, Radiation physics, Physics in Medical Imaging
S. Avramova-Cholakova, E. Kulama
Computed tomography (CT) has been proven to deliver high doses with a significant contribution to the collective effective dose of the population from medical exposure. A report of the European Commission reveals that mean effective doses from CT examinations in European countries vary from 0.3 mSv for Head in Moldova up to 50.5 mSv for Trunk in Denmark . The contribution of CT to the total collective effective dose from X-ray and nuclear medicine examinations for the group of countries from the European Union, Switzerland, Iceland and Norway is found to be 57%. The European Council Directive 2013/59/EURATOM requires Member States to establish, regularly review and use diagnostic reference levels (DRLs) as an important instrument for optimisation . The most recent UK guidance on the establishment of DRLs is available since 2004 . According to the recommended methodology, mean room dose has to be calculated “for a particular examination on a sample of close to standard-sized patients”. National DRLs (NDRLs) are established using the third-quartile values of the distributions of the mean doses. Local DRLs (LDRLs) can be established at hospital or Trust level for the purpose of further optimisation, based on the mean of the distribution of room mean doses in the organisation. Recently the International Commission on Radiological Protection (ICRP) issued Publication 135, providing updated recommendations on the establishment of DRLs . For the calculation of the typical dose, the use of the median value of the distribution of data from a room is recommended, and establishment of LDRLs and NDRLs based on the third-quartile values of the distributions of the medians is considered. A recent study confirmed the relevance of using medians instead of means, with recalculation of DRLs from older surveys . The present study at Imperial was initiated as a part of the fourth UK national patient dose survey in Computed Tomography. The purpose is to determine typical patient doses from seven CT scanners in the three hospitals of the Trust, to compare the examination protocols and to establish LDRLs according to the new ICRP recommendations.