title: Local diagnostic reference levels for typical radiographic procedures.
abstract: OBJECTIVE
  To establish local diagnostic reference levels (DRL) for typical radiographic examinations in a fully digital imaging institution.
  
  
  METHODS
  The initial survey included 6 standard radiographic projections performed in 19 computed radiography (CR) and digital radiography (DR) rooms. Because of the expected difference in the performance, the local reference levels were analysed separately for those 2 modalities. Data of 226 average size adult patients were included in the analysis. Entrance surface dose (ESD) was calculated from the recorded radiographic techniques and tube radiation output measurements. After observing wide variations in the results of the patient survey, the examinations were repeated by using anthropomorphic phantoms. Initial efforts to understand the reasons for dose variations were focused on CR chest, abdomen, pelvis, and lumbar spine examinations.
  
  
  RESULTS
  The average size patient doses for similar examinations were lower in the DR rooms than in the CR rooms by factors that ranged from 1.2 to 3, with the exception of the chest examination. Standardization of the CR exposure index value allowed us to decrease ESD by 21%-30%. Detector sensitivity had an insignificant effect (2%) on ESD; proper collimation lowered the dose by 17%. However, the major effect, up to 46% difference, was found because of antiscatter grids cutoff.
  
  
  CONCLUSIONS
  Modality specific local diagnostic reference levels for standard examinations have been established in a large digital imaging department with hybrid modalities. Typically the local reference values were lower than those recommended in Safety Code 35, except for CR chests. Factors that affect the dose variations have been investigated and determined.
authors.affiliation: Diagnostic Imaging Department, QE II Health Sciences Centre, Halifax, Nova Scotia, Canada. lena.Tonkopi@cdha.nshealth.ca
authors.forename: Elena
authors.initials: E
authors.lastname: Tonkopi
authors.forename: Cupido
authors.initials: C
authors.lastname: Daniels
authors.forename: Mary J
authors.initials: MJ
authors.lastname: Gale
authors.forename: Stephanie C
authors.initials: SC
authors.lastname: Schofield
authors.forename: Vicki A
authors.initials: VA
authors.lastname: Sorhaindo
authors.forename: Jeanne L
authors.initials: JL
authors.lastname: Vanlarkin
mesh_terms: D000328:Adult; D006801:Humans; D019047:Phantoms, Imaging; D011785:Quality Assurance, Health Care; D011829:Radiation Dosage; D011835:Radiation Protection / Q000592:standards; D011856:Radiographic Image Enhancement / Q000379:methods; D011859:Radiography / Q000592:standards*; D011873:Radiology Information Systems; D012016:Reference Values; D014057:Tomography, X-Ray Computed / Q000592:standards; D014963:X-Ray Intensifying Screens