title: Imaging characteristics evaluation of a digital radiography system.
abstract: OBJECTIVE
  To evaluate the physical imaging characteristics of an indirect digital radiography system used for general radiography.
  
  
  METHODS
  The performance of the two 41x41 cm2 CsI:Tl/a-Si flat-panel detectors of a GE-Revolution XR/d digital radiography system was evaluated. Signal uniformity, dose linearity, pre-sampling and expectation Modulation Transfer Function (MTF), Noise Power Spectrum (NPS) and Detective Quantum Efficiency (DQE) were measured at 70 kVp, varying the incident dose levels, according to IEC 62220-1. The effects of anti-scatter grid on NPS were also studied.
  
  
  RESULTS
  Both detectors have a limiting spatial resolution of 2.5 lp/mm set by the pixel pitch. Raw images demonstrated fairly good uniformity, excellent repeatability and linearity. Without the grid in the anode-cathode direction, for an 8 mGy incident dose, both pre-sampling and EMTF were greater than 0.5 and 0.2 for spatial frequencies of 1 and 2 lp/mm, respectively. At the same dose and frequencies, for one detector, DQE was greater than 0.61 and 0.20; for the other one, DQE was greater than 0.41 and 0.18.
  
  
  CONCLUSIONS
  The two detector panels showed different DQE curves. Namely, the table detector DQE was excellent at low dose levels but its performance appeared to degrade with increasing doses, both in mean values and in shape, whereas the wall stand detector DQE appeared to depend less strongly on dose. In any case, the DQE values obtained from this study were higher than those reported in the literature for storage phosphor Computed Radiography systems.
authors.affiliation: Servizio di Fisica Sanitaria, Fondazione Salvatore Maugeri, IRCCS, Istituto Scientifico di Pavia, Pavia. Italy. lmoro@fsm.it
authors.forename: Luca
authors.initials: L
authors.lastname: Moro
authors.forename: Armando
authors.initials: A
authors.lastname: Pannella
authors.forename: Chiara
authors.initials: C
authors.lastname: Bassetti
authors.forename: Daniele
authors.initials: D
authors.lastname: Fantinato
authors.forename: Maurizia
authors.initials: M
authors.lastname: Baldi
authors.forename: Giuseppe
authors.initials: G
authors.lastname: Bertoli
mesh_terms: D006801:Humans; D011856:Radiographic Image Enhancement / Q000295:instrumentation*; D012825:Silicon; D013673:Technology Assessment, Biomedical
chemical_list: D012825:Silicon