title: Alternative X-ray filters for an intra-oral digital radiographic system.
abstract: OBJECTIVE
  The aim of this study was to evaluate the effect of the modulation of the radiation spectrum with the use of alternative X-ray filters in the quality of intra-oral digital images from storage phosphor plates.
  
  
  METHODS
  The radiographic exposures were performed in a GE 1000 X-ray machine (General Electric Co., Milwaukee, WI), operating at 65 kVp, 10 mA, 40 cm focus receptor distance using three different exposure times: 0.05 s, 0.16 s and 0.35 s. The control filter (GC) was 100% aluminium (Al) with a thickness of 1.5 mm. The tested filters were: G1, 97% Al and 3% copper (Cu) with 1.47 mm thickness; G2, 96% Al and 4% Cu with 1.53 mm thickness; G3, 95% Al and 5% zinc (Zn) with 1.56 mm thickness; G4, 98% Al and 2% Zn with 1.5 mm thickness; and G5, 95% Cu and 5% Zn with 1.6 mm thickness. For formation of the image, a 12-step Al wedge (each step with increments of 1 mm in thickness) was radiographed 10 times. Pixel values measured in digital images were converted into optical density (OD).
  
  
  RESULTS
  All replicates showed OD with high reproducibility (r > 0.95) for all exposure times and tested filters. In comparison between filters, statistically significant differences in density (p < 0.05) were observed. The OD curve of the G5 filter in all exposure times and G3 filter in an exposure time of 0.05 s showed changes in shape (p < 0.05).
  
  
  CONCLUSIONS
  Excluding the G5 filter, all others tested filters can be used as a substitute for GC without losses in image quality.
authors.affiliation: Piracicaba Dental School of the State University of Campinas, Sao Paulo, Brazil.
authors.forename: J
authors.initials: J
authors.lastname: Stecke
authors.forename: A D
authors.initials: AD
authors.lastname: Cruz
authors.forename: S M
authors.initials: SM
authors.lastname: Almeida
authors.forename: F N
authors.initials: FN
authors.lastname: Bóscolo
mesh_terms: D000535:Aluminum; D003300:Copper; D004867:Equipment Design; D011857:Radiographic Image Interpretation, Computer-Assisted; D019252:Radiography, Dental, Digital / Q000295:instrumentation*; D012044:Regression Analysis; D014963:X-Ray Intensifying Screens; D014965:X-Rays; D015032:Zinc
chemical_list: D003300:Copper; D000535:Aluminum; D015032:Zinc