Establishing local and regional DRLs by means of electronic radiographical X-ray examination records

The objective of the paper is to demonstrate that patient dose audits may be undertaken at the local and regional levels by employing electronic examination records contained in Radiology Information Systems (RISs) that have been collected, analysed and managed by modern IT systems. The resulting mean and third quartile values obtained may then be used to establish local and regional dose reference levels (DRLs) as part of an optimisation strategy. The method involved the collection of roughly 1.3 million radiographical examination records stored in hospital RIS over a 3-y period from 10 hospital sites in the north of England. These were analysed according to the process employed in the national patient dose (NPD) audits undertaken every 5 y in the UK. Data processing and analysis methods are described that are suitable for handling very large data sets quickly and efficiently. Because RIS data involve manual data entry it may be susceptible to data entry errors. Therefore, a comparison of results obtained from both RIS and DICOM generated data was first of all undertaken in order to 'calibrate' the RIS-based method and demonstrate its accuracy. The results obtained from this comparison indicate that the RIS-based examination records provide patient dose distributions with an equivalent statistical accuracy compared with those employing DICOM data and, therefore, may be employed in patient dose audits in order to establish both local and regional DRLs for use in patient dose management and optimisation strategies.