title: A pilot evaluation of the R2 image checker system and users' response in the detection of interval breast cancers on previous screening films.
abstract: OBJECTIVE
  Breast screening radiologists are under considerable pressure to maximize cancer detection and minimize the number of interval cancers. This study used screening films, previously reported as normal, taken before the development of an interval cancer. The aim was to determine the sensitivity and specificity of the R2 Image Checker System and the responses of users in detecting abnormalities in these previous films.
  
  
  METHODS
  The first R2 Image Checker System in the U.K. was installed in the Canterbury Assessment Centre for evaluation purposes. System performance was compared with the standard protocol for assessing interval cancers used in the NHS Breast Screening Programme (NHSBSP) Three readers examined the previous films blind before switching on R2 and compared the prompts generated with the location of the subsequent interval cancer.
  
  
  RESULTS
  The previous screening films for 104 cases generated 134 R2 prompts on the subsequent cancer side and 109 on the non-cancer side. Readers classified 29 cancers as false-negative or minimal signs and R2 correctly prompted in 15 of these cases (52%). At least one reader rejected the correct prompt in five cases.
  
  
  CONCLUSIONS
  From this preliminary study it appears that R2 overprompts normal areas and underprompts some cancers in these difficult cases. A full multi-centre evaluation is needed to assess the possible contribution of R2 to the NHSBSP.
authors.affiliation: Department of Public Health Sciences, St George's Hospital Medical School, London, UK. linda.garvican@btinternet.com
authors.forename: L
authors.initials: L
authors.lastname: Garvican
authors.forename: S
authors.initials: S
authors.lastname: Field
mesh_terms: D000368:Aged; D001943:Breast Neoplasms / Q000000981:diagnostic imaging*; D002983:Clinical Competence; D003658:Decision Making, Computer-Assisted; D005188:False Negative Reactions; D005260:Female; D006801:Humans; D008327:Mammography; D008403:Mass Screening / Q000379:methods*; D008875:Middle Aged; D010865:Pilot Projects; D011857:Radiographic Image Interpretation, Computer-Assisted / Q000592:standards*; D012680:Sensitivity and Specificity