• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2003년도 추계학술대회 논문집 Vol.16
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• pp.427-430
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• 2003

The properties of digital X-ray detectors depend on the absorption extent of X-rays, the generated signal of each X-ray photon and the distribution of the generated signal between pixels. In digital X-ray detector with single layer, signal is generated by X-ray photon captured in photoconductor. In X-ray detector with multi structure that scintillator formed above the top of photoconductor, signal is generated both by X-ray photon captured each in scintillator and photoconductor. X-ray detector with multi structure is generated more signal than single layer detector. In this paper, we simulated absorption fraction of X-ray detector with multi-layer using Monte Carlo program. The results compared with single-layer detector to be formed scinillator or photoconductor.

• 대한의용생체공학회:의공학회지
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• 제29권5호
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• pp.364-370
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• 2008

Recent development in large area flat-panel x-ray detector technology enables clinical application of digital tomosyntesis. Unlike conventional motion tomography using x-ray films, flat-panel x-ray detectors provide projection images in digital formats so that tomographic images can be synthesized in a more flexible way. For the digital tomosynthesis, precise movements of the x-ray source and the x-ray detector with respect to a fulcrum point are necessary. In this study, we apply the digital tomosynthesis technique to the flat-panel detector based micro-CT in which the flat-panel detector and the x-ray source rotate together on a circular arc. The experimental results suggest that flat-panel detector based 3D CTs can be used for digital tomosynthesis in the clinical environment.

• 한국산학기술학회논문지
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• 제11권9호
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• pp.3517-3523
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• 2010

본 논문은 이중 에너지 DR(Digital Radiography) 방식 중, 단일 조사 X-선(single shot X-ray exposure) 장치와 이중 모드 검출기 모듈 (Low Energy Detector & High Energy Detector)을 이용한 이중 X-선 이미징이 가능한 검출기 모듈에 관한 연구이다. 상용 BIS(baggage inspection system)에서 사용되고 있는 X-선 발생장치의 스펙트럼과 이중 모드 검출기에 대한 특징 및 방사선적 특성을 분석하여 새롭게 제안 할 검출기 모듈의 최적 설계 방향을 기술하고 상용화된 용화된 LED 및 HED 검출기와 새롭게 제안 한 검출기 모듈에 대해 전기적, 광학적, 방사선적 특성 실험을 실시하여, 새롭게 제안된 검출기 모듈이 BIS 용도로 사용 가능함을 증명하였다. 새롭게 제안 된 검출기 모듈이 적용된 BIS에 대해, 기본 특성 실험에 대한 X-선 영상을 획득하여 실험 및 분석을 실시하였다.

• Transactions on Electrical and Electronic Materials
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• 제3권4호
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• pp.16-20
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• 2002

The high bias voltage associated with the thick layer (typically 500-1000 ㎛) of selenium required to have an acceptable x-ray absorption in radiography and fluoroscopy applications may have some practical inconvenience. A hybrid x-ray detector with zinc sulfide-amorphous selenium structure has been developed to improve the x-ray sensitivity of a a-Se based flat-panel digital imaging detector. Photoluminescence(PL) characteristic of a ZnS:Ag phosphor layer showed a light emission peak centered at about 450 nm, which matches the sensitivity spectrum of selenium. The dark current of the hybrid detector showed similar characteristics with that of a a-Se detector. The x-ray sensitivity of hybrid and a-Se x-ray detector was 345 pC/㎠/mR and 295 pC/㎠/mR at an applied voltage of 10 V/㎛, respectively. The purpose of this study was to evaluate the pertinence of a solution using a thin selenium layer, as a photosensitive converter, with a thick coating of silver doped zinc sulfide phosphor.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2002년도 춘계학술대회 논문집 센서 박막재료 반도체재료 기술교육
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• pp.31-34
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• 2002

In this paper, the electric properties of amophous selenium multilayer samples has been investigated. In order to develop the hybrid flat-panel digital· X-ray image detector, we measured and analyzed their performance parameters such as the X -ray sensitivity and dark-current for a amophous selenium multilayers X-ray detector with a phosphor layer, The hybrid digital X-ray image detector can be constructed by integrating a phosphor layer (or a scintillative layer) that convert X-ray to a light on a-Se photoconduction mulilayers that convert a light to electrical signal. As results, the dielectric materials such as parylene between the phosphor layer and the top electrode may reduce the dark-current of the samples. Amorphous selenium multilayers having dielectric layer(parylene) has characteristics of low dark-current, high X-ray sensitivity. So we can acquired a enhanced signal to noise ratio. In this paper offer the method can reduce the dark-current in the hybrid X-ray detector.

• Transactions on Electrical and Electronic Materials
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• 제4권3호
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• pp.10-14
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• 2003

In this paper, we have introduced the x-ray detector built with a CsI:Na scintillation layer deposited on amorphous selenium. To determine the thickness of the CsI:Na layer, we have estimated the transmission spectra and the absorption of continuous x-rays in diagnostic range by using computer simulation (MCNP 4C). A x-ray detector with 65 ${\mu}m$-CsI:Na/30 ${\mu}m$-Se layer has been fabricated by a thermal evaporation technique. SEM and PL measurements have been performed. The dark current and x-ray sensitivity of the fabricated detector has been compared with that of the conventional a-Se detector with 100 ${\mu}m$ thickness. Experimental results show that both detectors exhibit a similar dark current, which was of a low value below $400 pA/cm^2$ at 10 V/${\mu}m$. However, the CsI:Na-Se detector indicates high x-ray sensitivity, roughly 1.3 times that of a conventional a-Se detector. Furthermore, a CsI:Na-Se detector with an aluminium reflective layer shows a 1.8 times higher x-ray sensitivity than an a-Se detector. The hybrid type detector proposed in this work exhibits a low dark current and high x-ray sensitivity, and, in particular, excellent linearity to the x-ray exposure dose.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2002년도 추계학술대회 논문집 Vol.15
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• pp.395-398
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• 2002

Many research group started study to develope x-ray detector using thin film transistor from 1970. But realization of TFT based x-ray detector development was caused by progress of thin film transistor liquid crystal display(TFTLCD) device technology in 1990. The main current of TFT technology is display device. Research results expend TFT technology field from display device to sensor manufacture technology. These days many research group in the world realize various digital x-ray detector. In this study, We compare discharge erasing method to visible light erasing method in a-Se based digital x-ray detector. Visible light erasing method is known reset process in direct conversion x-ray detector. Digital x-ray detector using visible light erasing method is not adaptive for conventional x-ray device, because of its thickness. And it is not avaliable for real-time imaging for digital fluoroscopy, because of its long reset time. In this study we overcome these limitations and show new idea for real-time imaging method.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2002년도 하계학술대회 논문집 Vol.3 No.2
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• pp.853-856
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• 2002

Present. direct method x-ray conversion detector is studied by abroad medical instrument and country with amorphous Selenium. And we search the method for large area x-ray detector. Amorphous-Selenium based photoreceptor is widely used on the X-ray conversion materials. But amorphous-selenium based x-ray conversion detector is broken by high voltage and leakage defect point. In this paper, We investigated top-electrode distance rate to improve defect point and high voltage broken. The result to appoint to made large area x-ray conversion detector with base data.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2002년도 춘계학술대회 논문집 센서 박막재료 반도체재료 기술교육
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• pp.39-42
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• 2002

There is a renewed interest in the application of photoconductors especially Cd(Zn)Te to x-ray imaging. In this paper, We investigate effects on x-ray detection characteristic of Zn dopped CdTe detector. Cd(Zn)Te film was fabricated by vacuum thermal evaporation method and then investigate physical analysis using EPMA and XRD. We investigated the leakage current and X-ray photosensitivity as applied voltage about fabricated Cd(Zn)Te film. Experimental results showed that the increase of Zn dopped concentration in $Cd_{1-x}Zn_{x}Te$ detector reduced a leakage current and improved a signal to noise ratio significantly.

• Transactions on Electrical and Electronic Materials
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• 제5권4호
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• pp.133-137
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• 2004

The development of digital x-ray detector has been extensively progressed for the application of various medical modalities. In this study, we introduce a new hybrid-type x-ray detector to improve problems of a conventional direct or indirect digital x-ray image technology, which composed of multi-layer structure using a CaWO$_4$ phosphor and amorphous selenium (a-Se) photoconductor. The leakage current of our detector was found to be ∼180 pA/cm$^2$ at 10 V/m, which was significantly reduced than that of a single a-Se detector. The x-ray sensitivity was measured as the value of 4230 pC/cm$^2$/mR at 10 V/m. We found that the parylene thin film between a CaWO$_4$ phosphor and an a-Se layer acts as an insulator to prevent charge injection from indium thin oxide (ITO) electrode into an a-Se layer under applied bias.