title: A comparative study of a dual-energy-like imaging technique based on counting-integrating readout.
abstract: OBJECTIVE
  The recent introduction of a specific electronic readout chip, designed for the processing of the same signal pulses from an x-ray sensor in one integrating and one counting channel in each pixel E. Kraft et al., [IEEE Trans. Nucl. Sci. 54, 383-390 (2007)]; E. Kraft, "Counting and integrating microelectronics development for direct conversion X-ray imaging," Ph.D. thesis, 2007; J. Fink, "Characterization of the imaging performance of the simultaneously counting and integrating X-ray detector CIX," Ph.D. thesis, 2010, enables an alternative to conventional dual-energy imaging methods. As shown in a previous paper, the proposed alternative benefits from positively correlated noise in the raw data, inherent to the counting-integrating readout (CIX), which results in a reduction of basis image noise after dual-energy decomposition. In the present paper, the authors compare the new approach to dual-energy imaging to two conventional dual-energy techniques, the dual-kV technique and the dual-crystal technique and to a photon-counting technique based on two energy windows.
  
  
  METHODS
  The study is based on x-ray computed tomography (CT) simulations of an anthropomorphic head phantom, where the signal-to-noise ratios and the contrast-to-noise ratios in basis material images and quasi-monochromatic images at 60 keV are compared. Moreover, a simple pictorial illustration of the relevance of input noise correlations in the noise-propagation process during the dual-energy basis material decomposition are presented, as well as measurement data for the correlation obtained as a function of the x-ray flux rate.
  
  
  RESULTS
  Under the idealized assumptions of the absence of scatter and detector imperfections like K-escape, crosstalk and detector noise, our comparison shows that among the dual-energy techniques investigated, the CIX concept together with the dual-kV technique performs best, confirming the mitigating effect of correlated measurement data on the dual-energy basis material decomposition.
  
  
  CONCLUSIONS
  The novel concept of simultaneous counting of photons and integrating the x-ray energy flux has a large potential for dual-energy applications in both projection and tomographic x-ray imaging. Future work will have to focus on the sensitivity of the CIX dual-energy concept to scattered radiation, detector imperfections and high x-ray fluxes.
authors.affiliation: Philips Research Europe-Hamburg, 22335 Hamburg, Germany. ewald.roessl@philips.com
authors.forename: Ewald
authors.initials: E
authors.lastname: Roessl
authors.forename: Christoph
authors.initials: C
authors.lastname: Herrmann
authors.forename: Edgar
authors.initials: E
authors.lastname: Kraft
authors.forename: Roland
authors.initials: R
authors.lastname: Proksa
mesh_terms: D004867:Equipment Design; D019544:Equipment Failure Analysis; D006801:Humans; D007089:Image Enhancement / Q000295:instrumentation*; D007090:Image Interpretation, Computer-Assisted / Q000295:instrumentation*; D021621:Imaging, Three-Dimensional / Q000379:methods*; D010363:Pattern Recognition, Automated / Q000379:methods*; D019047:Phantoms, Imaging; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D012815:Signal Processing, Computer-Assisted / Q000295:instrumentation*; D018511:Systems Integration; D014057:Tomography, X-Ray Computed / Q000295:instrumentation*