title: The effects of image acquisition control of digital X-ray system on radiodensity quantification.
abstract: OBJECTIVE
  Aluminum step wedge (ASW) equivalent radiodensity (eRD) has been used to quantify restorative material's radiodensity. The aim of this study was to evaluate the effects of image acquisition control (IAC) of a digital X-ray system on the radiodensity quantification under different exposure time settings.
  
  
  METHODS
  Three 1-mm thick restorative material samples with various opacities were prepared. Samples were radiographed alongside an ASW using one of three digital radiographic modes (linear mapping (L), nonlinear mapping (N), and nonlinear mapping and automatic exposure control activated (E)) under 3 exposure time settings (underexposure, normal-exposure, and overexposure). The ASW eRD of restorative materials, attenuation coefficients and contrasts of ASW, and the correlation coefficient of linear relationship between logarithms of gray-scale value and thicknesses of ASW were compared under 9 conditions.
  
  
  RESULTS
  The ASW eRD measurements of restorative materials by three digital radiographic modes were statistically different (p = 0.049) but clinically similar. The relationship between logarithms of background corrected grey scale value and thickness of ASW was highly linear but attenuation coefficients and contrasts varied significantly among 3 radiographic modes. Varying exposure times did not affect ASW eRD significantly.
  
  
  CONCLUSIONS
  Even though different digital radiographic modes induced large variation on attenuation of coefficient and contrast of ASW, E mode improved diagnostic quality of the image significantly under the under-exposure condition by improving contrasts, while maintaining ASW eRDs of restorative materials similar. Under the condition of this study, underexposure time may be acceptable clinically with digital X-ray system using automatic gain control that reduces radiation exposure for patient.
authors.affiliation: Department of Restorative Science, University of Minnesota School of Dentistry, Minneapolis, MN, USA.
authors.forename: Wook-Jin
authors.initials: WJ
authors.lastname: Seong
authors.forename: Hyeon-Cheol
authors.initials: HC
authors.lastname: Kim
authors.forename: Soocheol
authors.initials: S
authors.lastname: Jeong
authors.forename: Youngcheul
authors.initials: Y
authors.lastname: Heo
authors.forename: Woo-Bin
authors.initials: WB
authors.lastname: Song
authors.forename: Mansur
authors.initials: M
authors.lastname: Ahmad
keywords: Aluminum step wedge equivalent radiodensity; Digital radiographic mode; Digital radiography; Image acquisition control; Image quality