title: Quality assurance system using statistical process control: an implementation for image cytometry.
abstract: OBJECTIVE
  Optical technologies have shown some promise for improving the care of cervical neoplasia. We are currently evaluating fluorescence and reflectance spectroscopy and quantitative cyto-histopathology for cervical neoplasia screening and diagnosis. Here we describe the establishment and application of a quality assurance (QA) system for detecting system malfunctions and assessing the comparability of four image cytometers used in a multicenter clinical trial.
  
  
  METHODS
  Our QA system involves three levels of evaluation based on the periodicity and complexity of the measurements. We implemented our QA system at three image cytometers at the British Columbia Cancer Agency and one at M.D. Anderson Cancer Center. The measurements or tasks were performed daily, monthly, and semi-annually. The current and voltage of the lamp, the calibration image characteristics, and the room temperature were checked daily. Long-term stability over time, short-term variability over time, and spatial response field uniformity were evaluated monthly. Camera linearity was measured semi-annually. Control charts based on statistical process control techniques were used to detect when the system did not perform optimally.
  
  
  RESULTS
  Daily measurements have shown good consistency in room temperature, lamp and calibration behaviour. Monthly measurements have shown small coefficients of variation between and within the four devices. There have been greater differences between sessions than within sessions. Comparability among the four systems is reasonably good. Semi-annual measurements have shown stable camera linearity. QA events were detected using the QA system. Multiple examples of event detection leading to correction of system malfunction are described in this report.
  
  
  CONCLUSIONS
  QA programs are critical for ensuring data integrity and therefore for the conduct of multicenter clinical trials.
authors.affiliation: Department of Cancer Imaging, British Columbia Cancer Agency, Vancouver, BC, Canada.
authors.forename: David
authors.initials: D
authors.lastname: Chiu
authors.forename: Martial
authors.initials: M
authors.lastname: Guillaud
authors.forename: Dennis
authors.initials: D
authors.lastname: Cox
authors.forename: Michele
authors.initials: M
authors.lastname: Follen
authors.forename: Calum
authors.initials: C
authors.lastname: MacAulay
mesh_terms: D005260:Female; D006801:Humans; D019044:Image Cytometry / Q000295:instrumentation*; D007091:Image Processing, Computer-Assisted; D008403:Mass Screening; D011785:Quality Assurance, Health Care / Q000379:methods*; D015203:Reproducibility of Results; D002583:Uterine Cervical Neoplasms / Q000175:diagnosis