title: Patient radiation dose management in dental facilities according to the X-ray focal distance and the image receptor type.
abstract: OBJECTIVE
  To determine particular reference values for patient radiation dose management according to the focus-to-skin distance and the image receptor type.
  
  
  METHODS
  Air-free ionization chambers and solid state detectors built in quality control devices were used to measure X-ray tube output in a sample of 2811 X-ray units. The mean exposure time was estimated by the local person responsible for the quality assurance programme. From this data, mean air kerma values were calculated at the focus-to-skin distance. To obtain the entrance surface air dose, a backscatter factor of 1.2 was used.
  
  
  RESULTS
  Third-quartile values were 5.3 mGy for old X-ray sets with around 10 cm focus-to-skin distance (FSD); for 20 cm FSD, the values were 4.1 mGy for D type, 3.4 mGy for E/F film type and 1.2 mGy for digital image receptors; and for 30 cm FSD the values were 2.1 mGy for D type, 1.8 mGy for E/F film type and 0.6 mGy for digital image receptors.
  
  
  CONCLUSIONS
  Evidence based on third-quartile values different from those expected justifies the need for particular reference values taking into account image system and focal distance, as a way to improve patient radiation dose management.
authors.affiliation: Department of Radiology, Medicine School, Complutense University, 28040 Madrid, Spain. luciano@med.ucm.es
authors.forename: L
authors.initials: L
authors.lastname: Gonzalez
authors.forename: J
authors.initials: J
authors.lastname: Moro
mesh_terms: D006801:Humans; D011829:Radiation Dosage; D011861:Radiography, Dental / Q000295:instrumentation* / Q000379:methods*; D019252:Radiography, Dental, Digital / Q000295:instrumentation; D011874:Radiometry / Q000379:methods; D012016:Reference Values; D012542:Scattering, Radiation; D014962:X-Ray Film; D014963:X-Ray Intensifying Screens