• Transactions on Electrical and Electronic Materials
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• v.3 no.2
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• pp.28-31
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• 2002

The Cdl-xZnxTe film was fabricated by thermal evaporation for the flat-panel X-ray detector. The stoichimetric ratio and the crystal structure of a polycrystalline Cd$_{1-x}$ Zn$_{x}$Te were investigated by EPMA and XRD, respectively. The leakage current and X-ray sensitivity of the fabricated films were measured to analyze the X-ray response characteristic of Zn in the polycrystalline CdZnTe thin film. The leakage current and the output charge density of Cd$_{0.7}$Zn$_{0.3}$Te thin film were measured to 0.37 nA/cm$^2$ and 260 pc/cm$^2$ at an applied voltage of 2.5 V/${\mu}{\textrm}{m}$, respectively. Experimental results showed that the increase of Zn doping rates in Cd$_{1-x}$ Zn$_{x}$Te detectors reduced the leakage current and improved the signal to noise ratio significantly.

• Proceedings of the KIEE Conference
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• 1997.07e
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• pp.1746-1748
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• 1997

The surface discharge type ac plasma display panel(ac PDP) is a flat display devices using gas discharge. In ac PDP, parallel electrodes covered with dielectric layer are on a substrates. The discharge current characteristics are affected by cell structure. In this study, the relationship between the principal design factor and discharge characteristics is discussed, based on experiment, and the current waveform is measured by voltage detector and storage O.S.C. as a parameter of design factor, e.g., electrode gap and width.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2002.11a
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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.

• Journal of Biomedical Engineering Research
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• v.29 no.5
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• pp.392-399
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• 2008

Thin-film transistor (TFT) arrays for an x-ray detector require quite different design concept from that of the conventional active-matrix liquid crystal devices (AM-LCDs). In this paper anew design of TFT array which uses only SiNx for passivation layer is described to meet the detector performance and the product availability simultaneously. For the purpose of optimizing the design parameters of the TFT array, a Spice simulation was performed. As a result, some parameters, such as the TFT width, the data line capacitance, and the storage capacitance, were able to be fixed. The other parameters were decided within a permissible range of the TFT process especially the photolithography process and the wet etch process. Then we adapted the TFT array which had been produced by the proposed design to our prototype model (FDXD-1417 and evaluated it clinically by comparing with a commercial model (EPEX, Hologic, Beford, USA). The results say that our prototype model is slightly better than EPEX system in chest PA images. So we can prove the technical usefulness and the commercial values of the proposed TFT design.

• Journal of the Korea Safety Management & Science
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• v.17 no.4
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• pp.213-221
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• 2015

The aim of this study was to set up the optimal exposure condition according to detector type considering image quality (IQ) with radiation dose in chest digital radiography. We used three detector type such as flat-panel detector (FP) and computed radiography (CR), and charge-coupled device (CCD). Entrance surface dose (ESD) was measured at each exposure condition combined tube voltage with tube current using dosimeter, after attaching on human phantom, it was repeated 3 times. Phantom images were evaluated independently by three chest radiologists after blinding image informations. Standard exposure condition using each institution was 117 kVp-AEC at FP and 117 kVp-8 mAs at CR, and 117 kVp-8 mAs at CCD. Statistical analysis was performed by One way ANOVA (Dunnett T3 test) using SPSS ver. 19.0. In FP, IQ scores were not significant difference between 102 kVp-4 mAs and 117 kVp-AEC (28.4 vs. 31.1, p=1.000), even though ESD was decreased up to 50% ($62.3{\mu}Gy$ vs. $125.1{\mu}Gy$). In CR, ESD was greatly decreased from 117 kVp-8 mAs to 90 kVp-8 mAs without significant difference of IQ score (p=1.000, 24.6 vs. 19.5). In CCD, IQ score of 117 kVp-8 mAs was similar with 109 kVp-8 mAs (29.6 vs. 29.0), with decreasing from $320.8{\mu}Gy$ to $284.7{\mu}Gy$ (about 11%). We conclude that optimal x-ray exposure condition for chest digital radiography is 102 kVp-4 mAs in FP and 90 kVp-8 mAs in CR, and 109 kVp-8 mAs in CCD.

• Journal of the Institute of Electronics Engineers of Korea SC
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• v.40 no.3
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• pp.163-171
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• 2003

To evaluate the performance of the digital radiography(DR) system developed in our group, the modulation transfer function(MTF) was measured and compared with that of an analog X- ray detector, film/screen system. The DR system has an amorphous selenium(a-Se) layer vacuum-evaporated on a TFT flat panel detector. The speed class 400 film/screen (Fuji) system has been being used in the clinical field as analog X-ray detectors. Both the square wave and slit method were used to evaluate their MTF. The square method was applied to both film/screen and the DR system. The slit method, however, was applied to only DR system. The full-width half maximum resolution of film/screen was 357${\mu}{\textrm}{m}$(1.4 lp/mm at 50% spatial frequency), and the resolution of DR was limited to 200${\mu}{\textrm}{m}$(2.5 lp/mm at 30%). These results indicate the measured resolution limitations approximate to the pixel pitch, 139 ${\mu}{\textrm}{m}$ of TFT. The MTF of DR is higher than that of film/screen by the factor of 1.785. It is proved that our a-Se based DR system has potential usefulness in the clinical field.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2005.11a
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• pp.254-255
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• 2005

In this paper, we investigated electrical characteristics of the X-ray detector of mercuric iodide (HgI2) film fabricated by PIB(Particle-in-Binder) Method on ITO substrates 17cm$\times$20cm in size with thicknesses ranging from approximately 200${\mu}m$ to 240${\mu}m$. In the present study, using I-V measurements, their electrical properties such as leakage current, X-ray sensitivity, and signal-to-noise ratio (SNR),were investigated. The results of our study can be useful in the future design and optimization of direct active-matrix flat-panel detectors (AMFPD) for various digital X-ray imaging modalities.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2002.11a
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• pp.379-382
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• 2002

Lately, intensifying screen of the $CaWO_4$ is used to medical treatment and diagnosis of the image. In this paper, we investigated transmission fraction and mass attenuation coefficient of $CaWO_4$ screen about diagnostic x-ray of low energy using MCNP 4C code. Experimentally, for 0.9 mm-$CaWO_4$ screen, the absorbable rate of diagnostic x-ray is more than 95%. according to kVp, the experimental value of mass attenuation coefficient is in a1most agreement with an corrected estimate value of MCNP and the deviation of experimental values is less than ${\pm}7%$. Using the MCNP code through this paper, we can make an estimate of signal and design for construction of the CaWO4/a-Se based digital x-ray image detector and make a good use of the foundation data for development of other materials.

• Transactions on Electrical and Electronic Materials
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• v.4 no.5
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• pp.15-18
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• 2003

The Cd$\_$1-x/Zn$\_$x/Te film was produced by thermal evaporation for the flat-panel X-ray detector. The crystal structure and the surface morphology of poly crystalline Cd$\_$1-x/Zn$\_$x/Te film were examined using XRD and SEM, respectively. The leakage current and X-ray sensitivity of the fabricated films were measured to analyze the X-ray response characteristic of Zn in a polycrystalline CdZnTe thin film. The leakage current and the output charge density of Cd$\_$0.7/Zn$\_$0.3/Te thin film were measured to 0.3 1nA/$\textrm{cm}^2$ and 260 pC/$\textrm{cm}^2$ at an applied voltage of 2.5 V/$\mu\textrm{m}$, respectively. Experimental results showed that the increase of Zn doping rates in Cd$\_$1-x/Zn$\_$x/Te detectors reduced the leakage current and improved the X-ray sensitivity significantly. The leakage current was drastically diminished by the formation of thin parylene layer in the Cd$\_$0.7/Zn$\_$0.3/Te detector.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.18 no.8
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• pp.60-66
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• 2019

This study aims to develop and manufacture a device for inspecting impurities in a sealed aluminum container using an X-ray technique. Two X-ray oscillators and detectors are used to detect the entire sample. The stage for sample movement was fabricated using two high-voltage generators and X-ray detectors arranged diagonally. In addition, the high-voltage generator is composed of a vacuum tube, a high-voltage generator, and circulating oil for cooling. It includes a control unit for controlling other equipment, a power supply unit, and a video output unit; the most important part of the X-ray is the X-ray generation part. In this study, a flat panel was used along with the aim of developing the detector part. In particular, the development of the scintillator introduced in this study is a primary focus. The developed scintillator can be combined with a lens and can then be assembled with a charge coupled device (CCD) sensor.