title: Measurement accuracy: a comparison of two intra-oral digital radiographic systems, RadioVisiography-S and FlashDent, with analog film.
abstract: OBJECTIVE
  To compare the accuracy of measurement algorithms incorporated into the software provided with two CCD-based digital radiographic systems and compare assessments using intra-oral film.
  
  
  METHODS
  A test object with three radiopaque reference points was imaged using Ektaspeed intra-oral film, both with and without an overlaid 1 mm reference grid, the RVG-S, the measurement software of which overlays a 2 mm grid, and the FlashDent, which uses a mouse-driven cursor to estimate distances. Geometric factors, including source-to-object and receptor-to-object distances, vertical and horizontal cone angulation, and vertical angulation of receptor, were successively altered. Six viewers estimated vertical, horizontal and diagonal distances for each image.
  
  
  RESULTS
  Increased source-to-object distance resulted in a 5-10% reduction in image dimensions, whereas increased receptor-to-object distance produced a magnification of 15-20% with all techniques. Increased vertical and horizontal cone angulation resulted in slight increases in magnification (0-5%) whereas greater receptor angulation resulted in noticeable magnification under all test conditions (10-15%). Estimated values for vertical, horizontal and diagonal measurements were approximately 5-10% higher than the actual dimensions, irrespective of the technique used. The FlashDent mouse-driven cursor system and direct measurement of distances from conventional film were more accurate in horizontal and diagonal dimension estimates than using an overlaid grid. Intra-observer and inter-observer differences were found for specific situations.
  
  
  CONCLUSIONS
  The mouse-driven computerized measurement cursor and intra-oral film assessment using a ruler provided the most accurate, reliable and consistent dimensional measurements.
authors.affiliation: University of Louisville School of Dentistry, Kentucky, USA.
authors.forename: W C
authors.initials: WC
authors.lastname: Scarfe
authors.forename: S
authors.initials: S
authors.lastname: Norton
authors.forename: A G
authors.initials: AG
authors.lastname: Farman
mesh_terms: D000704:Analysis of Variance; D015588:Observer Variation; D011856:Radiographic Image Enhancement; D011857:Radiographic Image Interpretation, Computer-Assisted; D011858:Radiographic Magnification; D019252:Radiography, Dental, Digital; D015203:Reproducibility of Results