Sci-Fri AM(1): Imaging-05: Setting Local Diagnostic Reference Levels

Abstract

OBJECTIVE To establish local diagnostic reference levels (DRLs) for typical radiographic examinations in a fully digital imaging institution, and to compare these to values published in Health Canada's Safety Code 35A. METHODLOGY Standard radiographic projections performed in twenty radiographic rooms at six different hospital sites were evaluated. Six rooms employed Digital (DR) units and fourteen rooms employed Computed Radiography(CR) systems. Except for four CR rooms in which technical factors were set manually, all rooms employed automatic exposure control. Analysis included data of 342 average adult patients and anthropomorphic phantoms. Entrance surface doses were calculated from tube radiation output measurements. RESULTS Typically, average patient doses for similar examinations were lower in the DR rooms than the CR rooms by factors ranging from of 1.2 to 3.1. Variations for the same examination performed in different rooms DR rooms were relatively small, but ranged by up to 7.9 times for CRimaging. Initial efforts to understand the reasons for the variations focused on Chest, Abdomen and Lumbar Spine examinations. The major reason identified was varying reference Exposure Index values which were accepted for images of diagnostic quality. CONCLUSION For Chest, Abdomen, and Lumbar Spine radiographic examinations local DRLs for DR systems were set lower than that for CR systems, and all DRL's were set lower than those recommended in Safety Code 35A, except for CR chests. Future work includes further optimization of all standard radiographic and fluoroscopic examinations.