title: Comparison of image quality indicators among mammography facilities in Ontario.
abstract: OBJECTIVE
  To compare the technical aspects of image quality of mammography machines in facilities across Ontario.
  
  
  METHODS
  Eight mammographic physics consultants took measurements and calculated accreditation phantom scores, mean glandular dose, entrance exposure, average optical density, half value layer and the limiting resolution of the imaging chain for 100 mammography machines across Ontario.
  
  
  RESULTS
  Of the 100 machines, 39 were affiliated with the Ontario Breast Screening Program (OBSP), and the remaining 61 were applying to become OBSP affiliates. All of the OBSP facilities and 32 of the applicants were accredited with the Mammography Accreditation Program (MAP) of the Canadian Association of Radiologists (CAR). All OBSP facilities had passing phantom scores, and 84% of the applicants with CAR accreditation and 79% of those without had passing phantom scores. The mean glandular dose was 1.5 (range 1.0-1.9, standard deviation [SD] 0.22) mGy for OBSP facilities, 1.3 (0.8-1.8, SD 0.29) mGy for CAR accredited and 1.4 (0.9-1.9, SD 0.24) mGy for nonaccredited applicants. Mean entrance exposures were 798 (540-1280, SD 135) mR, 717 (430-980, SD 153) mR and 770 (520-930, SD 116) mR for the OBSP, accredited and nonaccredited facilities respectively. There were no appreciable differences in the mean optical densities (approx. 1.62 OD), mean half-value layers (approx. 0.34 mm Al) or mean resolutions measured with the large focal spot (nominal size of 0.3 mm) either parallel (approx. 16 line pairs/mm) or perpendicular (approx. 14 line pairs/mm) to the cathode-anode axis of the x-ray tube, among the 3 types of facilities.
  
  
  CONCLUSIONS
  Image quality is increased and variability is decreased in facilities participating in a province-wide screening program.
authors.affiliation: Sunnybrook and Women's College Health Sciences Centre, Room S657, 2075 Bayview Ave., Toronto, ON M4N 3M5.
authors.forename: N L
authors.initials: NL
authors.lastname: Ford
authors.forename: M J
authors.initials: MJ
authors.lastname: Yaffe
mesh_terms: D000068:Accreditation; D005260:Female; D006801:Humans; D008327:Mammography / Q000295:instrumentation / Q000706:statistics & numerical data*; D008403:Mass Screening / Q000295:instrumentation / Q000706:statistics & numerical data*; D009864:Ontario; D019047:Phantoms, Imaging; D011785:Quality Assurance, Health Care; D011829:Radiation Dosage; D012015:Reference Standards