title: Detective quantum efficiency of photon-counting x-ray detectors.
abstract: OBJECTIVE
  Single-photon-counting (SPC) x-ray imaging has the potential to improve image quality and enable novel energy-dependent imaging methods. Similar to conventional detectors, optimizing image SPC quality will require systems that produce the highest possible detective quantum efficiency (DQE). This paper builds on the cascaded-systems analysis (CSA) framework to develop a comprehensive description of the DQE of SPC detectors that implement adaptive binning.
  
  
  METHODS
  The DQE of SPC systems can be described using the CSA approach by propagating the probability density function (PDF) of the number of image-forming quanta through simple quantum processes. New relationships are developed to describe PDF transfer through serial and parallel cascades to accommodate scatter reabsorption. Results are applied to hypothetical silicon and selenium-based flat-panel SPC detectors including the effects of reabsorption of characteristic/scatter photons from photoelectric and Compton interactions, stochastic conversion of x-ray energy to secondary quanta, depth-dependent charge collection, and electronic noise. Results are compared with a Monte Carlo study.
  
  
  RESULTS
  Depth-dependent collection efficiency can result in substantial broadening of photopeaks that in turn may result in reduced DQE at lower x-ray energies (20-45 keV). Double-counting interaction events caused by reabsorption of characteristic/scatter photons may result in falsely inflated image signal-to-noise ratio and potential overestimation of the DQE.
  
  
  CONCLUSIONS
  The CSA approach is extended to describe signal and noise propagation through photoelectric and Compton interactions in SPC detectors, including the effects of escape and reabsorption of emission/scatter photons. High-performance SPC systems can be achieved but only for certain combinations of secondary conversion gain, depth-dependent collection efficiency, electronic noise, and reabsorption characteristics.
authors.affiliation: Robarts Research Institute, Western University, London, Ontario N6A 5C1, Canadaand Department of Medical Biophysics, Western University, London, Ontario, N6A 3K7, Canada.
authors.forename: Jesse
authors.initials: J
authors.lastname: Tanguay
authors.affiliation: Biomedical Engineering Program, Western University, London, Ontario, N6A 3K7, Canadaand School of Mechanical Engineering, Pusan National University, Jangjeon-dong, Geumjeong-gu, Busan 609-73, South Korea.
authors.forename: Seungman
authors.initials: S
authors.lastname: Yun
authors.affiliation: School of Mechanical Engineering, Pusan National University, Jangjeon-dong, Geumjeong-gu, Busan 609-73, South Korea.
authors.forename: Ho Kyung
authors.initials: HK
authors.lastname: Kim
authors.affiliation: Robarts Research Institute, Western University, London, Ontario N6A 5C1, Canada; Department of Medical Biophysics, Western University, London, Ontario, N6A 3K7, Canada; and Biomedical Engineering Program, Western University, London, Ontario, N6A 3K7, Canada.
authors.forename: Ian A
authors.initials: IA
authors.lastname: Cunningham
mesh_terms: D009010:Monte Carlo Method; D017785:Photons; D011336:Probability; D011789:Quantum Theory; D011859:Radiography / Q000295:instrumentation* / Q000379:methods*; D013269:Stochastic Processes; D014965:X-Rays