title: A new clinical unit for digital radiography based on a thick amorphous selenium plate: physical and psychophysical characterization.
abstract: OBJECTIVE
  Here, we present a physical and psychophysical characterization of a new clinical unit (named AcSelerate) for digital radiography based on a thick a-Se layer. We also compared images acquired with and without a software filter (named CRF) developed for reducing sharpness and noise of the images and making them similar to images coming from traditional computed radiography systems.
  
  
  METHODS
  The characterization was achieved in terms of physical figures of merit [modulation transfer function (MTF), noise power spectra (NPS), detective quantum efficiency (DQE)], and psychophysical parameters (contrast-detail analysis with an automatic reading of CDRAD images). We accomplished measurements with four standard beam conditions: RAQ3, RQA5, RQA7, and RQA9.
  
  
  RESULTS
  The system shows an excellent MTF (about 50% at the Nyquist frequency). The DQE is about 55% at 0.5 lp/mm and above 20% at the Nyquist frequency and is almost independent from exposure. The contrast-detail curves are comparable to some of the best published data for other systems devoted to imaging in general radiography. The CRF filter influences both the MTF and NPS, but it does lead to very small changes on DQE. Also the visibility of CDRAD details is basically unaltered, when the filter is activated.
  
  
  CONCLUSIONS
  As normally happens with detector based on direct conversion, the system presents an excellent MTF. The improved efficiency caused by the thick layer allows getting good noise characteristics and DQE results better (about 10% on average) than many of the computed radiography (CR) systems and comparable to those obtained by the best systems for digital radiography available on the market.
authors.affiliation: Alma Mater Studiorum, Physics Department, University of Bologna, 40127 Bologna, Italy.
authors.forename: Stefano
authors.initials: S
authors.lastname: Rivetti
authors.forename: Nico
authors.initials: N
authors.lastname: Lanconelli
authors.forename: Marco
authors.initials: M
authors.lastname: Bertolini
authors.forename: Domenico
authors.initials: D
authors.lastname: Acchiappati
mesh_terms: D006801:Humans; D019047:Phantoms, Imaging; D011601:Psychophysics; D011856:Radiographic Image Enhancement / Q000295:instrumentation*; D012643:Selenium; D012984:Software
chemical_list: D012643:Selenium