Cascaded-systems analysis of sandwich x-ray detectors

Abstract

Active sandwich-like multilayer detectors have been developed, and their potential for motion-artifact-free dual-energy x-ray imaging at a single exposure has been demonstrated in the material decomposition context. Since the sandwich detector uses the x-ray beam transmittance through the front layer, direct x-ray interaction within photodiodes in the front layer is unavoidable, and which can increase noise in the front detector images. Similar direct x-ray interaction can also occur in the rear detector layer. To obtain a better contrast performance, an additional filter layer can be placed between the two detector layers. However, this filter layer can increase adversely noise in images obtained from the rear detector layer by reducing the number of x-ray photons reaching it. A theoretical model, which can describe the signal-to-noise performance of the sandwich detector as functions of various design parameters, has been developed by using a linear cascaded-systems theory. From the cascaded-systems analysis, the direct x-ray interaction increases noise at the high spatial frequencies where the number of secondary quanta lessens. The intermediate filter layer enhances the contribution of additive electronic noise in the overall noise performance of the rear detector layer. The detailed cascaded-systems analysis on the x-ray sandwich detectors are reported in comparisons with the measured noise-power spectra and detective quantum efficiencies. The developed model will be useful for a better design and practical use of a sandwich detector for single-shot dual-energy imaging. K: Detector design and construction technologies and materials; Detector modelling and simulations I (interaction of radiation with matter, interaction of photons with matter, interaction of hadrons with matter, etc); X-ray radiography and digital radiography (DR)1He is now affiliated with the Samsung Electronics Co.

Noise-reduction approaches to single-shot dual-energy imaging with a multilayer detector

“…The effects of noise-reduction methods on the contrast were negligible. As shown by line plots, the theoretical estimation using the cascaded-systems analysis (CSA) [7,14,23] is also included in figure 4. The error bars in the line plots represent the CSA results for ±10% variations in material thickness to account for the uncertainties in Al and PU material properties (e.g.…”

“…atomic number and composition) and thickness for an intermediate filter [13], but those optimal figures will be dependent upon detector materials/thickness as well as application-specific tasks (including energies). Theoretical cascadedmodel analysis approach may be helpful for a better design of sandwich detector [10,14,15].…”

Linear analysis of single-shot dual-energy computed tomography with a multilayer detector

“…A schematic diagram and a CAD drawing depicting the sandwich detector are also included in figure 1. The operation of bench-top system, including fabrication and working principle of the sandwich detector, can be found in our previous papers in detail [7,9,10]. Briefly, the front and rear detector layers employ the same photodiode array, which is based on the complementary metal-oxidesemiconductor active-pixel sensor technology and features a 0.048-mm-sized pixel arranged in a 512 × 1024 format.…”

“…For a larger energy separation, interlayer filter can be placed in-between two detector layers. Since the rear detector layer measures x-ray photons with relatively higher energies survived from the attenuation through the front detector/filter layers, the use of a thicker scintillator, compared to the front scintillator, is typical [8,9]. In a previous study [10], we successfully showed demonstration bone-selective CT images for a postmortem mouse using the sandwich detector.…”

Development of a large-area multilayer detector for single-shot dual-energy imaging

“…The combination of the phosphor and photodiode array layers for the indirect flat-panel detector configuration has an advantage in terms of design flexibility and performance optimization because two parts of phosphor and photodiode are physically separate and the corresponding x-ray conversion and light conversion are independent to each other [13]. A theoretical framework describing the signal and noise generation in the sandwich detector has been introduced [14], and the approach will be useful to design a detector in terms of various detector design and operation parameters (e.g. the intermediate filter material/thickness and the applied tube voltage or kVp).…”