title: Distribution of scattered radiation during intraoral radiography with the patient in supine position.
abstract: OBJECTIVE
  The purpose of this study was to investigate the spatial distribution of scattered radiation during intraoral radiography with the patient in a supine position to determine the exposure to an operator without a suitable barrier.
  
  
  METHODS
  A phantom was placed in the supine position on a dental chair with the occlusal plane perpendicular to the floor, and four intraoral periapical radiographic examinations in the anterior and posterior regions of the maxilla and mandible were performed. The scattered radiation was measured with an ionization chamber at distances ranging from 25 to 200 cm at 25 cm increments and at intervals of 45 degrees. Measurements were made at two different heights: level with the occlusal plane and 30 cm below it. The exposure was converted to an air-kerma/absorbed dose in air.
  
  
  RESULTS
  The distribution of scattered radiation was symmetric during examinations of the anterior region. Circular iso-exposure curves of up to 0.5 microGy were observed at the level of the occlusal plane, and curves of up to 0.1 microGy were observed 30 cm below the plane. The lowest exposures were measured 30 cm below the occlusal plane and behind the chair. The distribution of scattered radiation was not symmetric during examinations of the posterior region. Iso-exposure curves of up to 0.25 microGy were observed at the level of the occlusal plane during exposure of the maxilla, and curves of up to 0.5 microGy were observed during exposure of the mandible. Circular iso-exposure curves of up to 0.1 microGy were observed 30 cm below the occlusal plane. Lower values for scattered radiation were observed 30 cm below the occlusal plane between 135 and 180 degrees behind the phantom.
  
  
  CONCLUSIONS
  The spatial distribution of scattered radiation with the patient in a supine position was not the same in eight directions around the chair. Although the preferred position for the operator is behind a suitable barrier, the preferred position in the absence of a barrier is 200 cm behind the patient.
authors.affiliation: Department of Oral and Maxillofacial Radiology, Tokyo Dental College, Japan.
authors.forename: K
authors.initials: K
authors.lastname: Kuroyanagi
authors.forename: Y
authors.initials: Y
authors.lastname: Hayakawa
authors.forename: H
authors.initials: H
authors.lastname: Fujimori
authors.forename: T
authors.initials: T
authors.lastname: Sugiyama
mesh_terms: D003727:Dental Auxiliaries; D006801:Humans; D016273:Occupational Exposure; D019047:Phantoms, Imaging; D011829:Radiation Dosage; D011861:Radiography, Dental / Q000379:methods*; D011874:Radiometry; D012542:Scattering, Radiation; D016683:Supine Position