• Journal of the Korean Society of Radiology
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• v.8 no.7
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• pp.429-433
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• 2014

In this study, the morphology and the x-ray quantum efficient of mercury oxide (HgO) and lead oxide (PbO) sensors derived by particle sedimentation method were discussed. In the pursuit of this purpose, we investigated the electrical characteristics and the x-ray quantum efficiency of various thicknesses of HgO and PbO films in mammographic x-ray energy. We have therefore developed a particle-in-binder sedimentation method of fabricating large area polycrystalline films onto transparent glass substrates coated with indium tin oxide. We are currently optimizing the growth method to improve the quantum efficiency with the ultimate goal of obtaining as quantum efficiency close to that of single crystal performance. Our future efforts will concentrate on optimization of large area film growth techniques specifically for deposition on a-Si:H flat panel readout arrays.

• Journal of the Korean Society of Radiology
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• v.5 no.5
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• pp.283-287
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• 2011

In this study, fine $Gd_2O_2S$:Tb powder was synthesized by using a low temperature solution-combustion method for a high-resolution digital x-ray imaging detector. From the fabricated phosphor power, the fine scintillator films was fabricated by particle sedimentation method and was investigated the luminescent property. From the experimental results of relative light output as a function of terbium concentration, the highest luminescent efficiency has at 5 wt% Tb concentration, and luminescent intensity decreased rapidly according to quenching effect about higher Tb concentration. Also, the relative light output of $270{\mu}m$-$Gd_2O_2S$:Tb film has 2945 pC/$cm^2$/mR. And light intensity was saturated at higher film thickness. Finally, to evaluate an image acquisition performance of fabricated phosphor, images were obtained by using commercial CMOS sensor and measured the MTF, NPS, and DQE. DQE(0 lp/mm) of fine phosphor film has 37%. But, DQE improvement of fine phosphor film is possible by resolving problem of film fabrication process and has a significant potential in the application of digital radiation imaging system later.

• Journal of the Institute of Electronics and Information Engineers
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• v.51 no.12
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• pp.189-194
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• 2014

In this study, from a new x-ray detector that combines a columnar CsI:Na scintillation layer with a photosensitive mercuric iodide layer was investigated. In this structure, X-rays are converted into visible light on a thick CsI:Na layer, which is then converted to electric charges in a thin $HgI_2$ bottom layer. The thin coplanar mercuric iodide films as a photosensitive converter requiring only a few tens of volts of bias, associated with a thick columnar coating of phosphor layer, were simulated and designed. The results of this research suggest that the new coplanar x-ray detector with a hybrid-type structure can resolve the following problems: high voltage from the a-Se, and low conversion efficiency from the indirect conversion method. The results of this research suggest that the new CsI:Na/$HgI_2$ x-ray detector with a double-layer type structure can resolve the following problems: high voltage from the direct conversion method, and low conversion efficiency from the indirect conversion method.

• Journal of the Korean Society of Radiology
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• v.3 no.4
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• pp.29-33
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• 2009

Recently, the compound materials(a-Se, $HgI_2$, PbO, CdTe, $PbI_2$, etc.) that are used in flat panel x-ray imager have been studied for digital x-ray imaging. In this paper, the signal detection properties of $HgI_2$ and a-Se conversion layer, are compared. The thick $HgI_2$ film is fabricated by special particle-in-binder method and the conventional vacuum thermal evaporation is used for a deposition of a-Se film. And an electrical characteristic measurements were investigated about leakage current, signal response property and x-ray sensitivity. From the experimental results show that the $HgI_2$ film has a low operation voltage and high signal generation than that of a-Se.

• Journal of the Korean Society of Radiology
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• v.17 no.3
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• pp.459-464
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• 2023

Due to the development of advanced technology, a lot of digital radiographic equipment has been developed, which is very helpful for accurate diagnosis and treatment, and it is very important to train personnel who have acquired professional knowledge in order to use it safely and effectively. Students are exposed to the risk of radiation exposure in radiography training using diagnostic X-ray equipment, and some educational institutions do not use X-ray equipment due to management difficulties in accordance with the Nuclear Safety Act. As a solution to this, this study developed a medical radiation simulator for education that does not generate radiation by using a vision sensor and self-developed software. Through this, educational institutions can reduce the burden of administrative implementation according to the law, and students can obtain a high level of educational effects in a healthy practice environment without radiation exposure.

• Journal of the Korean Society of Radiology
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• v.9 no.2
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• pp.67-72
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• 2015

In diagnostic radiology, the use of automatic exposure control device is internationally recommended for diagnosis and optimization. However, if exposed to prolonged radiation is a complicated manufacturing process, there is a problem that occurs decrease of various performance overall brightness sensor, which is commercially available conventional. Therefore, in this study, absorption of X-ray is high, and I want to evaluate the AEC applicability of the sensor of the photoconductor-based production has an easy advantage. Experimental results confirms the possibility of fabrication of the sensor through an increase in the SNR, with the detection efficiency superior, accurate turn-off. In addition, it is confirmed that the experimental results of the transmittance and the latent image, Ghost effect by the light conductor does not appear, in the case of a photoconductor with the exception of the PbO, 80% - and it was confirmed good transmittance of 90%. Therefore, excellent mechanical stability and poor performance due to a change of the doping concentration than the existing products that have been put to practical use, the sensor easy photoconductor based, fabrication and can be applied as AEC sensor is expected.

• Journal of Sensor Science and Technology
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• v.4 no.4
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• pp.62-69
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• 1995

We have developed the digital radiography system applied by the one dimensional multiwire proportional chamber. X-ray position signals were obtained from anode wires which were connected to counters through amplifiers and discriminators. The chamber was made of gas flow type and detector gas was P10. The threshold voltage which gives to the discriminator is independent on the neighboring channels. This improved the uniformity of the detector. Then the differential nonlineality is ${\pm}4%$. Increasing the gas pressure, the spatial resolution is about 1.4-mm at which the pitch of the anode wire is 2-mm. The object is scanned in vertical direction to take an image. The number of pixels in the image is $32{\times}32$.

• Progress in Medical Physics
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• v.15 no.4
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• pp.202-209
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• 2004

Flat panel based digital radiography (DR) systems have recently become useful and important in the field of diagnostic radiology. For DRs with amorphous silicon photosensors, CsI(TI) is normally used as the scintillator, which produces visible light corresponding to the absorbed radiation energy. The visible light photons are converted into electric signal in the amorphous silicon photodiodes which constitute a two dimensional array. In order to produce good quality images, detailed behaviors of DR detectors to radiation must be studied. The relationship between air exposure and the DR outputs has been investigated in many studies. But this relationship was investigated under the condition of the fixed tube voltage. In this study, we investigated the relationship between the DR outputs and X-ray in terms of the absorbed energy in the detector rather than the air exposure using SPEC-l8, an X-ray energy spectrum model. Measured exposure was compared with calculated exposure for obtaining the inherent filtration that is a important input variable of SPEC-l8. The absorbed energy in the detector was calculated using algorithm of calculating the absorbed energy in the material and pixel values of real images under various conditions was obtained. The characteristic curve was obtained using the relationship of two parameter and the results were verified using phantoms made of water and aluminum. The pixel values of the phantom image were estimated and compared with the characteristic curve under various conditions. It was found that the relationship between the DR outputs and the absorbed energy in the detector was almost linear. In a experiment using the phantoms, the estimated pixel values agreed with the characteristic curve, although the effect of scattered photons introduced some errors. However, effect of a scattered X-ray must be studied because it was not included in the calculation algorithm. The result of this study can provide useful information about a pre-processing of digital radiography.

• Journal of Sensor Science and Technology
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• v.11 no.1
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• pp.9-17
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• 2002

The forming conditions of X-ray storage phosrhors $BaFBr_{1-x}I_x:Eu^{2+}$, $Na^+$ have been investigated, and measured the PSL emission spectra and its intensity, fading characteristics and does dependence of the prepared phosphors. These characteristics were compared with those of commercial image plate (ST-III) obtained from Fuji Photo Film Co. The optimal preparing conditions of $BaFBr_{1-x}I_x:Eu^{2+}$, $Na^+$ Phosphor were 0.5 mol% of $EuF_3$, 4.0 mol% of NaF and composition ratio x=0.3, and the sintering temperature were $950^{\circ}C$ in $H_2$ atmosphere. When the composition ratio x was equal to 0, the spectral range of the luminescence of $BaFBr_{1-x}I_x:Eu^{2+}$, $Na^+$ phosphor was $365{\sim}420\;nm$, and its maximum luminescence intensity appeared at 390 nm. When composition ratio x was not equal to 0, the wavelength ranges and peak of the spectra were shifted to the longer wavelength with the growth of composition ratio x. A good linearity was shown between the PSL intensity and X-ray irradiation dose. The phosphor sample with x=0.3 exhibited better fading characteristics than that of other $BaFBr_{1-x}I_x:Eu^{2+}$ phosphor samples, and the fading characteristics of the PSL intensity at room temperature were shown poorer with increasing $I^-$ ion concentration. The lattice constant of the phosphor becomes larger with increasing the $I^-$ ion concentration.

• Journal of the Institute of Electronics and Information Engineers
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• v.53 no.5
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• pp.143-151
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• 2016

The aim of this study is to investigate the optimal algorithm to extract medical radiation induced pixel signal from complementary metal-oxide semiconductor (CMOS) sensors of smartphones camera. The pixel intensity and pixel number of smartphone camera were measured as the X-ray dose was increased. The front camera of the smartphone camera has low noise property and excellent dose response as compared to the back camera of the smartphone. The indirect method which uses scintillation crystal in front of the smartphone camera, couldn't improve the X-ray detection efficiency as compared to the direct method which does not use any scintillator in front of the smartphone camera. When we used the algorithm which employing threshold level on the pixel intensity and pixel number, the dose linearity was more higher for the pixel intensity rather for the pixel number. The use of pixel intensity of Y color component which represents the grey scale, would be efficient in terms of the radiation detection efficiency and reducing the complexity of the image processing. We expect that the radiation dose monitoring can be managed effectively and systematically by using the proposed radiation detection algorithm, thus eventually will contribute to the public healthcare.