Diagnostic Reference Levels in Computer Tomography at IPOCFG, EPE

Abstract

In this work we estimated the doses related to the Computer Tomography (CT) for the most frequent clinical examination protocols at the Radiology Department of the Oncology Institute of Coimbra. The dose evaluation methodology followed the European Guidelines. We determined Diagnostic Reference Levels (DRL) in terms of one slice, (Volume) Weighted Computed Tomography Dose Index - (CTDI_vol) CTDI_w, and in terms of complete exam, Dose Length Product - DLP for 3 CT scanners: Siemens Somaton Plus 4, GE HiSpeed LX/i and Siemens Somaton Sensation Open. The results were compared with the European Reference Levels EUR 16262 and with MSCT Bongartz (2004). A sample of 225 adult patients, both male and female, of standard size was selected, with a minimum of 10 patients for each clinical protocol and CT scanner. Local DRL’s were assigned as the average of the results for the 3 CT scanners. In general, DRL results are below the European reference levels for all protocols except thoracic, lumbar and sacrum spine. Additionally, effective doses were determined with the ImPACT’s CT dosimetry spreadsheet and were compared with those published in ICRP 102. To give more accessible information to the patient and physician, we converted the effective doses in terms of background equivalent radiation time (BERT) using the World average annual dose of 2.4 mSv/year.