title: Contrast-detail phantom study for x-ray spectrum optimization regarding chest radiography using a cesium iodide-amorphous silicon flat-panel detector.
abstract: OBJECTIVE
  The purpose of this study evaluating a cesium iodide-amorphous silicon-based flat-panel detector was to optimize the x-ray spectrum for chest radiography combining excellent contrast-detail visibility with reduced patient exposure.
  
  
  METHODS
  A Lucite plate with 36 drilled holes of varying diameter and depth was used as contrast-detail phantom. For 3 scatter body thicknesses (7.5 cm, 12.5 cm, 21.5 cm Lucite) images were obtained at 113 kVp, 117 kVp, and 125 kVp with additional copper filter of 0.2 and 0.3 mm, respectively. For each setting, radiographs acquired with 125 kVp and no copper filter were taken as standard of reference. On soft-copy displays, 3 observers blinded to the exposure technique evaluated the detectability of each aperture in each image according to a 5-point scale. The number of points given to all 36 holes per image was added. The scores of images acquired with filtration were compared with the standard images by means of a multivariate analysis of variance. Radiation burden was approximated by referring to the entrance dose and calculated using Monte Carlo method.
  
  
  RESULTS
  All 6 evaluated x-ray spectra resulted in a statistically equivalent contrast-detail performance when compared with the standard of reference. The combination 125 kVp with 0.3 mm copper was most favorable in terms of dose reduction (approximately 33%).
  
  
  CONCLUSIONS
  Within the constraints of the presented contrast-detail phantom study simulating chest radiography, the CsI/a-Si system enables an addition of up to 0.3 mm copper filtration without the need for compensatory reduction of the tube voltage for providing constant image quality. Beam filtration reduces radiation burden by about 33%.
authors.affiliation: Department of Diagnostic Radiology, University Hospital of Regensburg, Regensburg, Germany. o.hamer@gmx.de
authors.forename: Okka W
authors.initials: OW
authors.lastname: Hamer
authors.forename: Markus
authors.initials: M
authors.lastname: Völk
authors.forename: Niels
authors.initials: N
authors.lastname: Zorger
authors.forename: Ingitha
authors.initials: I
authors.lastname: Borisch
authors.forename: Roland
authors.initials: R
authors.lastname: Büttner
authors.forename: Stefan
authors.initials: S
authors.lastname: Feuerbach
authors.forename: Michael
authors.initials: M
authors.lastname: Strotzer
mesh_terms: D002586:Cesium; D003198:Computer Simulation; D003287:Contrast Media; D006801:Humans; D007454:Iodides; D019047:Phantoms, Imaging; D011829:Radiation Dosage; D011856:Radiographic Image Enhancement / Q000295:instrumentation; D013902:Radiography, Thoracic / Q000295:instrumentation*; D012825:Silicon; D014963:X-Ray Intensifying Screens
chemical_list: D003287:Contrast Media; D007454:Iodides; D002586:Cesium; C040050:cesium iodide; D012825:Silicon