title: Light source-induced error in computer-assisted image analysis with a video-based system.
abstract: OBJECTIVE
  We tested the hypothesis that two different light sources, an alternating current fluorescent viewbox and a direct current halogen viewbox, do not differ with respect to their ability to illuminate reproducibly a radiograph during image capture.
  
  
  METHODS
  Two radiographs were taken: one with four hydroxyapatite chips mounted against a dry mandible and one without the chips. They were digitally subtracted with a video-based imaging system. The procedure was repeated at different times.
  
  
  RESULTS
  A statistically significant difference among optical density measurements was found when the alternating current fluorescent viewbox (p < 0.001) was used and was related to light intensity variation. Such effect was not observed with the direct current halogen viewbox (p = 0.873).
  
  
  CONCLUSIONS
  Study design efficiency was increased by 212% with the use of the direct current halogen viewbox so that to detect a specified treatment effect with a given level of statistical confidence, the sample size has to be 2.12 times greater if the alternating current fluorescent viewbox is used.
authors.affiliation: College of Dentistry, Department of Periodontology, University of Florida, Gainesville, USA.
authors.forename: F A
authors.initials: FA
authors.lastname: Stutz
authors.forename: A F
authors.initials: AF
authors.lastname: Hefti
authors.forename: C H
authors.initials: CH
authors.lastname: Gibbs
mesh_terms: D015502:Absorptiometry, Photon; D000704:Analysis of Variance; D016477:Artifacts; D003951:Diagnostic Errors; D006801:Humans; D008027:Light; D008029:Lighting / Q000379:methods*; D008334:Mandible / Q000000981:diagnostic imaging; D011856:Radiographic Image Enhancement / Q000379:methods*; D011861:Radiography, Dental / Q000379:methods*; D015203:Reproducibility of Results; D013382:Subtraction Technique / Q000295:instrumentation*; D014741:Video Recording