title: Diagnostic Reference Levels and Monitoring Practice Can Help Reduce Patient Dose From CT Examinations.
abstract: OBJECTIVE
  The purpose of this study is to establish provincial diagnostic reference levels (DRLs) and to determine whether this process may help reduce the patient radiation dose from the most frequently performed CT examinations.
  
  
  METHODS
  We investigated the following CT examinations: head, chest, low-dose chest, abdomen and pelvis, and chest, abdomen, and pelvis examinations. The sample for each protocol included 15 patients of average body weight (mean [± SD], 70 ± 20 kg). The differences in dose between scanners were evaluated using one-way ANOVA. Correlations between dose, scanner age, and the number of detector rows were assessed using the Pearson correlation coefficient. A sample of abdominal and chest examinations were randomized and blinded for review by experienced radiologists who graded diagnostic image quality. Provincial DRLs were calculated as the 75th percentile of patient dose distributions. For hospitals with doses exceeding the DRLs, dose reduction was recommended, followed by another survey.
  
  
  RESULTS
  The initial survey included data of 1185 patients, and an additional 180 patients were surveyed after protocol optimization. The differences between the mean values of the dose distributions from each scanner were statistically significant (p < 0.05) for all examinations. The variation was greatest for low-dose chest CT, with a greater than fivefold difference in the mean dose values noted between scanners. A very weak correlation was found between dose and scanner age or the number of detector rows. Analysis of image quality revealed no statistically significant differences in any scoring categories, with the exception of the noise category in abdominal imaging. Implementation of the DRLs allowed a reduction in patient dose of up to 41% as a result of a protocol change.
  
  
  CONCLUSIONS
  Establishing provincial DRLs allows an effective reduction in patient dose without resulting in degradation of image quality.
authors.affiliation: 1 Department of Diagnostic Radiology, Dalhousie University, 1276 South Park St, PO Box 9000, Halifax, NS B3H 2Y9, Canada.|2 Department of Diagnostic Imaging, Nova Scotia Health Authority, Halifax, NS, Canada.
authors.forename: Elena
authors.initials: E
authors.lastname: Tonkopi
authors.affiliation: 1 Department of Diagnostic Radiology, Dalhousie University, 1276 South Park St, PO Box 9000, Halifax, NS B3H 2Y9, Canada.|2 Department of Diagnostic Imaging, Nova Scotia Health Authority, Halifax, NS, Canada.
authors.forename: Susan
authors.initials: S
authors.lastname: Duffy
authors.affiliation: 1 Department of Diagnostic Radiology, Dalhousie University, 1276 South Park St, PO Box 9000, Halifax, NS B3H 2Y9, Canada.|2 Department of Diagnostic Imaging, Nova Scotia Health Authority, Halifax, NS, Canada.
authors.forename: Mohamed
authors.initials: M
authors.lastname: Abdolell
authors.affiliation: 1 Department of Diagnostic Radiology, Dalhousie University, 1276 South Park St, PO Box 9000, Halifax, NS B3H 2Y9, Canada.|2 Department of Diagnostic Imaging, Nova Scotia Health Authority, Halifax, NS, Canada.
authors.forename: Daria
authors.initials: D
authors.lastname: Manos
mesh_terms: D000368:Aged; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D009674:Nova Scotia; D011829:Radiation Dosage; D011835:Radiation Protection / Q000379:methods*; D011874:Radiometry / Q000379:methods*; D012016:Reference Values; D014057:Tomography, X-Ray Computed / Q000295:instrumentation*
keywords: CT dose optimization; diagnostic reference levels