Premium
A comparative study of a dual‐energy‐like imaging technique based on counting‐integrating readout
Author(s) -
Roessl Ewald,
Herrmann Christoph,
Kraft Edgar,
Proksa Roland
Publication year - 2011
Publication title -
medical physics
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.473
H-Index - 180
eISSN - 2473-4209
pISSN - 0094-2405
DOI - 10.1118/1.3651643
Subject(s) - photon counting , noise (video) , detector , imaging phantom , energy (signal processing) , optics , physics , signal to noise ratio (imaging) , pixel , computer science , artificial intelligence , quantum mechanics , image (mathematics)
Purpose: 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.