Experimental evaluation of a novel CdZnTe flat-panel x-ray detector for digital radiography and fluoroscopy

Tokuda, S.; Adachi, Susumu; Sato, Toshiyuki; Yoshimuta, Toshinori; Nagata, Hisashi; Uehara, K.; Izumi, Yuichi; Teranuma, Osamu; Yamada, S.

doi:10.1117/12.430924

Cited by 27 publications

(14 citation statements)

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“…This injection of charge corresponds to a 70 keV photon interacting with a cadmium zinc telluride (CZT) detector with a work function (i.e., the average amount of energy required to produce an electron-hole pair) of 4.6 eV (Limousin, 2003). The input capacitor was assumed to be 1×1 mm 2 with a 500 μm thick (Tokuda et al , 2001) dielectric (consisting of CZT) having a relative permittivity of 10. The gain of the amplifier can vary, as discussed below, but a signal magnitude between 1.25 and 2 V (a range expected to be sufficient to allow good comparator performance) was desired.…”

Section: Methodsmentioning

confidence: 99%

Performance of in-pixel circuits for photon counting arrays (PCAs) based on polycrystalline silicon TFTs

et al. 2016

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Photon counting arrays (PCAs), defined as pixelated imagers which measure the absorbed energy of x-ray photons individually and record this information digitally, are of increasing clinical interest. A number of PCA prototypes with a 1 mm pixel-to-pixel pitch have recently been fabricated with polycrystalline silicon (poly-Si) — a thin-film technology capable of creating monolithic imagers of a size commensurate with human anatomy. In this study, analog and digital simulation frameworks were developed to provide insight into the influence of individual poly-Si transistors on pixel circuit performance — information that is not readily available through empirical means. The simulation frameworks were used to characterize the circuit designs employed in the prototypes. The analog framework, which determines the noise produced by individual transistors, was used to estimate energy resolution, as well as to identify which transistors contribute the most noise. The digital framework, which analyzes how well circuits function in the presence of significant variations in transistor properties, was used to estimate how fast a circuit can produce an output (referred to as output count rate). In addition, an algorithm was developed and used to estimate the minimum pixel pitch that could be achieved for the pixel circuits of the current prototypes. The simulation frameworks predict that the analog component of the PCA prototypes could have energy resolution as low as 8.9% FWHM at 70 keV; and the digital components should work well even in the presence of significant TFT variations, with the fastest component having output count rates as high as 3 MHz. Finally, based on conceivable improvements in the underlying fabrication process, the algorithm predicts that the 1 mm pitch of the current PCA prototypes could be reduced significantly, potentially to between ~240 and 290 μm.

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Section: Methodsmentioning

confidence: 99%

Performance of in-pixel circuits for photon counting arrays (PCAs) based on polycrystalline silicon TFTs

et al. 2016

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“…To overcome this problem, materials of high atomic numbers and densities, such as mercuric iodide (HgI 2 ), lead iodide (PbI 2 ) [6][7][8][9][10][11], lead oxide (PbO) [12], thallium bromide (TlBr) [13], and cadmium telluride/cadmium zinc telluride (CdTe/CdZnTe) [14][15][16][17], have been suggested to replace a-Se. All of these materials possess effective ionization energy about 10 times lower than that of a-Se, substantially large band gaps, necessary for minimization of leakage currents at room temperature, and high mobility-lifetime product, providing effective charge collection [9,18,19].…”

Section: Introductionmentioning

confidence: 99%

Performance of Large Area Thin-Film CdTe Detector in Diagnostic X-Ray Imaging

Shvydka¹,

Jin²,

Parsai³

2013

IJMPCERO

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Significant advancement in thin-film cadmium telluride (CdTe) deposition techniques in recent years has made this material attractive for the development of low-cost large area detector. Here we evaluate the intrinsic performance of the detector for a range of energies relevant to diagnostic imaging applications, such as fluoroscopy. The input x-ray spectra for a set of tube potentials ranging from 70 to 140 kVp were computed with the tungsten anode spectral model using interpolating polynomials (TASMIP) based on the measured output of our diagnostic x-ray simulator. Frequency-dependent detector performance analysis was conducted through Monte Carlo simulations of energy deposition within the detector. Intrinsic modulation transfer functions (MTF), noise power spectra (NPS), and detective quantum efficiencies (DQE) were computed for a set of CdTe detectors of varying thickness, from 100 to 1000 μm. MTF behavior at higher frequencies was affected by thickness and input energy, NPS increased with film thickness and energy, and the resultant DQE(f) decreased with increasing the input energy, but increased with the thickness of the detector. We found that the optimal thickness of CdTe under diagnostic x-ray beam is in the range of 300 to 600 μm. Physical properties of CdTe, such as the high atomic number and density, used in direct detection configuration, together with the recently established thin-film manufacturing techniques makes this technology a promising photoconductor for largearea diagnostic flat panel imaging.

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“…1 Introduction CdTe and Cd 1-x Zn x Te (CZT) have attracted attention as room temperature X-ray and γ-ray detectors, because they have an inherently high stopping power of X-ray and γ-ray, a good carrier-transport property, and relatively wide band-gap energy [1][2][3][4][5]. However, it would be difficult to apply single-crystal CdTe and CZT detectors to large-area flat panel X-ray detectors.…”

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confidence: 99%

“…Furthermore, it is well-known that Cl-doping is very important for obtaining high resistivity and passivating grain boundary [2,3,12,14]. Therefore, we used a mixture of CdTe, ZnTe and CdCl 2 powder as a source material for the CSS deposition of the Cl-doped CZT [6,7].…”

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Deposition of Cl‐doped CdTe polycrystalline films by close‐spaced sublimation

Okamoto

Takahashi

Akiba

et al. 2015

Phys. Status Solidi C

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The effects of Cl‐doping on the CdTe layers by the close‐spaced sublimation (CSS) deposition were investigated. Cl‐doped CdTe polycrystalline films were deposited on graphite substrates by CSS method using a mixture of CdTe and CdCl2 powder as a source. In X‐ray diffraction (XRD) patterns of the obtained films with various deposition times, many diffraction peaks other than CdTe peaks were observed in the deposition times lower than 10 min. These diffraction peaks were probably due to the formation of chlorides of Cd, Te and C, such as CdCl2, TeCl4, Te3Cl2 and C10Cl8. X‐ray fluorescence (XRF) and secondary ion mass spectrometry (SIMS) analyses revealed that a large amount of chlorine was contained in the films with the deposition times lower than 10 min, and that Cl concentration decreased with increasing the deposition time above 3 min. These results indicate that the films containing the chlorides of Cd, Te and C in addition to CdTe are formed in the initial stage of the CSS deposition using a mixture of CdTe and CdCl2 powder as a source. Cross‐sectional images revealed that the grain size was decreased by the effect of Cl‐doping. Furthermore, current‐voltage (I ‐V) characteristics of the CdTe/graphite structures were measured, and it was found that the resistivity of the Cl‐doped CdTe layer was much higher than that of the undoped CdTe layer. (© 2015 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

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Experimental evaluation of a novel CdZnTe flat-panel x-ray detector for digital radiography and fluoroscopy

Cited by 27 publications

References 0 publications

Performance of in-pixel circuits for photon counting arrays (PCAs) based on polycrystalline silicon TFTs

Performance of in-pixel circuits for photon counting arrays (PCAs) based on polycrystalline silicon TFTs

Performance of Large Area Thin-Film CdTe Detector in Diagnostic X-Ray Imaging

Deposition of Cl‐doped CdTe polycrystalline films by close‐spaced sublimation

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