Establishment of a comprehensive set of regional DRLs for CT by means of electronic X-ray examination records.

The International Commission on Radiological Protection (ICRP) has indicated that the diagnostic reference level (DRL) has the optimisation of protection as its objective for diagnostic and interventional procedures [International Commission on Radiological Protection. Protection against ionising radiation from external sources: ICRP Report 105 (2007)]. An important aim of this paper was to demonstrate a straightforward and cost-effective mechanism for undertaking patient dose audits that can be employed in the production of local and regional DRLs for use by medical physics experts in the provision of scientific support services to diagnostic radiology. The process developed employs electronic X-ray examination records obtained from multiple hospital sites transferred to a central processing and reporting facility. Results of a large-scale audit of patient doses resulting from CT examinations are presented. Doses are expressed in terms of dose length product (DLP) and were collected by remotely accessing electronic examination records held in hospital radiology information systems. Data were collected from 18 hospital sites involving up to 123 different types of examinations covering an ∼18-month period from July 2011 to December 2012. In total, 177 000 CT examination records were collected. Values have been validated against equivalent records obtained from digital imaging and communications in medicine (DICOM) header data and found to be in excellent statistical agreement. Extremely large variations in DLP values were noted for many examinations when data for all scanners were pooled. Results are discussed in relation to other surveys and differences highlighted in terms of the variations in methodologies employed and the numbers of examination records investigated. A mechanism for establishing DRLs is proposed, which could help to unify mechanisms for establishing DRLs for CT examinations.