• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2012.10a
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• pp.997-999
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• 2012

Digital X-ray image detector is widely used for radiodiagnosis. Amorphous selenium has been received attention as one of the major material that confirmed photoconductor of direct methode detector. We analysis the photocurrent using 2-dimensional device simulator when blue-ray (${\lambda}=486nm$) is irradiated and high voltage is biased. We evaluate electron-hole generation rate, electron-hole recombination rate, and electron/hole distribution in the amorphous selenium. This simulation methode is helpful to the analysis of digital X-ray image detector. We expect that many applications will be developed in digital X-ray image detector using 2-dimensional device simulator.

• Journal of the Institute of Electronics and Information Engineers
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• v.49 no.10
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• pp.187-193
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• 2012

Digital X-ray image detector has been applied for medical and industrial fields. Photoconductors have been used to convert the X-ray energy to electrical signal on the direct digital X-ray image detector and amorphous selenium (a-Se) has been used as a photoconductor, normally. In this work, we use 2-dimensional device (2-D) simulator to study about physical phenomena in the a-Se, when we irradiate electromagnetic radiation (${\lambda}=486nm$) on the a-Se surface. We evaluate the electron-hole generation rate, electron-hole recombination rate, and electron/hole distribution in the a-Se using 2-D simulator. This simulator divides the device into triangle and calculates using interpolation method. This simulation method has been proposed for the first time and we expect that it will be applied for the development of digital X-ray image detector.

• Journal of radiological science and technology
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• v.34 no.1
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• pp.9-15
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• 2011

In this paper, an image quality evaluation of amorphous selenium based x-ray system was performed using modulation transfer function (MTF) measurement. MTF as a main factor of imaging quality evaluation was investigated by contrast method from acquired test pattern image. The MTF value was measured to 36.1% at 3.0 lp/mm which is twice as high as that in the film image. Compared with other studies, the results demonstrate that amorphous selenium based x-ray detector is clinically meaningful.

• Proceedings of the Materials Research Society of Korea Conference
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• 2003.11a
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• pp.206-206
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• 2003

• Proceedings of the Materials Research Society of Korea Conference
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• 2002.11a
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• pp.120-120
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• 2002

• Proceedings of the Materials Research Society of Korea Conference
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• 2002.11a
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• pp.128-128
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• 2002

• Journal of radiological science and technology
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• v.26 no.4
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• pp.39-46
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• 2003

Digital radiographic systems based on solid-state detectors, commonly referred to as flat-panel detectors, are gaining popularity in clinical practice. Large area, flat panel solid state detectors are being investigated for digital radiography. The purpose of this work was to evaluate the active matrix flat panel digital x-ray detectors in terms of their modulation transfer function (MTF), noise power spectrum (NPS), and detective quantum efficiency (DQE). In this paper, development and evaluation of a selenium-based flat-panel digital x-ray detector are described. The prototype detector has a pixel pitch of $139\;{\mu}m$ and a total active imaging area of $14{\times}8.5\;inch^2$, giving a total 3.9 million pixels. This detector include a x-ray imaging layer of amorphous selenium as a photoconductor which is evaporated in vacuum state on a TFT flat panel, to make signals in proportion to incident x-ray. The film thickness was about $500\;{\mu}m$. To evaluate the imaging performance of the digital radiography(DR) system developed in our group, sensitivity, linearity, the modulation transfer function(MTF), noise power spectrum (NPS) and detective quantum efficiency(DQE) of detector was measured. The measured sensitivity was $4.16{\times}10^6\;ehp/pixel{\cdot}mR$ at the bias field of $10\;V/{\mu}m$ : The beam condition was 41.9\;KeV. Measured MTF at 2.5\;lp/mm was 52%, and the DQE at 1.5\;lp/mm was 75%. And the excellent linearity was showed where the coefficient of determination ($r^2$) is 0.9693.

• Progress in Medical Physics
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• v.19 no.4
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• pp.219-226
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• 2008

In this study, we have conducted characterization of imaging performance for a flat panel digital X-ray detector using amorphous Selenium and a-Si TFT which was developed by the authors. The procedures for characterization were in concordance with internationally recommended standards such as IEC (international electrotechnical commission). The measures used for imaging performance characterization include response characteristic, modulation transfer function (MTF), detective quantum efficiency (DQE), noise power spectrum (NPS), and quantum limited performance. The measured DQEs at lowest and highest spatial frequencies were 40% and 25% respectively, which was superior to that of commercial products by overseas vendor. The MTF values were significantly superior to that of CR and indirect type DRs. The quantum limited performance showed the detector was limited by quantum noise at the entrance exposure level below 0.023 mR, which is sufficiently low for general X-ray examination.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2006.11a
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• pp.282-283
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• 2006

The transport phenomena of arsenic (As) doped amorphous selenium(a-Se:As) thin film for digital X-ray conversion material has been reported. The effect of As addition on the carrier mobility and recombination lifetime in a-Se:As sample has been measured using the moving photo-carrier grating (MPG) technique. An Increase in hole mobility and recombination was observed when 0.3% arsenic, was added into a-Se sample, whereas electron mobility decrease with arsenic addition due to the defect density. The fabricated a-Se:03% As device exhibited the highest X-ray sensitivity.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2001.11b
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• pp.505-508
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• 2001

Currently there is much interested in removing latent charge that is caused to latent image effect and blurring of obtained image as well as reduction of x-ray conversion efficiency in digital radiography system. To remove latent charge a-Se film is irradiated by light with 3500 lux using halogen lamp and optical fiber. We measured dark current and photosensitivity to analyze removing effect of latent charge, then compared with and without light erasing method. The reduction of measured signal due to latent charge effect was 32.5 %, and the removal effect of latent charge by using light erase method was its 95.5 %.