• Proceedings of the Korean Society of Medical Physics Conference
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• 2002.09a
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• pp.407-410
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• 2002

Monochromatic x-ray CT has several advantages over conventional CT, which utilizes bremsstrahlung white x-rays from an x-ray tube. There are several methods to produce such monochromatic x-rays. The most popular one is crystal diffraction monochromatization, which has been commonly used because of the fact that the energy spread is very narrow and the energy can be changed continuously. The alternative method is the use of fluorescent x-ray, which has several advantages such as large beam size and fast energy change. We have developed a parallel-beam and a fan-beam monochromatic x-ray CT, and compared some characteristics such as accuracy of CT numbers between those systems. The fan beam monochromatic x-rays were generated by irradiating target materials by incident white x-rays from a bending magnet beam line NE5 in 6.5 GeV Accumulation Ring at Tukuba. The parallel beam monochromatic x-rays were generated by using a silicon double crystal monochromator at the bending magnet beam line BL-20BM in Spring-8. A Cadmium telluride (CdTe) 256 channel array detector with 512mm sensitive width capable of operating at room temperature was used in the photon counting mode. A cylindrical phantom containing eight concentrations of gadolinium was used for the fan beam monochromatic x-ray CT system, while a phantom containing acetone, ethanol, acrylic and water was used for the parallel monochromatic x-ray CT system. The linear attenuation coefficients obtained from CT numbers of those monochromatic x-ray CT images were compared with theoretical values. They showed a good agreement within 3%. It was found that the quantitative measurement can be possible by using the fan beam monochromatic x-ray CT system as well as a parallel beam monochromatic X-ray CT system.

• Journal of the Korean Society of Radiology
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• v.15 no.1
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• pp.71-78
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• 2021

When continuous X-ray are used when acquiring and X-ray image, even the same material may not be accurately represented in the image according to the thickness due to various X-ray energies. To solve this problem, the X-ray energy spectrum was changed to improve the image quality. Using SPEKTR v3.0, an X-ray energy spectrum with an additional filter added and a general X-ray energy spectrum using only a unique filter were obtained. Simulation was performed using the obtained X-ray energy spectrum as a radiation source for Geant4 Application for Tomographic Emission (GATE). Using GATE data, an X-ray image with an additional filter and an image reconstructed from and X-ray image without an additional filter were compared and analyzed through a mono energy image of 74 keV. In the case of using the X-ray energy spectrum without using an additional filter, the amount of X-rays transmitted according to the thickness of the same material is different from the amount that decreases according to the thickness of the material. Similar results were obtained as the amount decreased with the material thickness. In other words, a similar result was obtained when the reduced dose was used with a mono energy. When an X-ray image is obtained by changing an X-ray energy spectrum using an additional filter, a more accurate result of transmission of X-rays may be obtained. In radiological examination, it was confirmed that the appropriate use of the additional filter has a great effect on improving the image quality.

• 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 Korean Academy of Oral and Maxillofacial Radiology
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• v.8 no.1
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• pp.39-42
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• 1978

The effect of irradiation of x-ray to developing rat mandible in the gestation stage was focused on the study of mandible development and the side effect of x-ray irradiation. The author studied the effect of x-ray irradiation with the gestated rat and their off'springs. 100 rads, 200 rads, 300 rads and 400 rads of x-ray was irradiated in regular order schematically at the lower left abdomen of gestated rat. 18½days after conception, their off'springs were sacrificed and exaimined their developing mandible with histological findings. The results were as followed. 1. In the 100-200 rads irradiated rat off'springs, bony trabeclulation was revealed irregular shape. In combine with this finding, osteoblast and fibroblast were appeared shrunken of their nucleus and location of eccentric position. 2. In the 300-400 rads irradiated rat off'springs, decrease of fibroblast and osteoblast appearance in the periosteum were prominently observed and empty lacunae were frequently appeared in their bone matrix. 3. The advent of osteoclast and resorption of cortical bone were appeared in proportion to increasing of x-ray irradiation.

• Journal of Korean Academy of Oral and Maxillofacial Radiology
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• v.20 no.2
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• pp.289-297
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• 1990

The purpose of this study was to assess the resolution and focal spot size of dental X-ray machines. Fifty dental X-ray machines were selected for measuring resolution and focal spot size. These machines were used in general dental clinics. The time of installation of the X-ray machine varies from 1 year to 10 years. The resolution of these machines was measured with the test pattern. The focal spot size of these machines was measured with the star test pattern. The following results were obtained: 1. The resolution of dental intraoral X-ray machines was not significantly changed in ten years. 2. The focal spot size of dental intraoral X-ray machines was not significantly increased in ten years. The statistical analysis between the mean focal spot size and nominal focal spot size was significant at the 0.05 level about the more than 3 years used machines.

• Proceedings of the Optical Society of Korea Conference
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• 1998.08a
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• pp.192-193
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• 1998

At Rutherford Appleton Laboratory(RAL), a high-repetition rate ps exicmer laser-plasma x-ray source has been developed for x-ray lithography with a calibrated output of up to 1 watt X-ray average power at 1nm wavelength. In a previous reports this compact x-ray source was used to print 0.18$\mu$m lines for a gate on Si-FET devices and deep three-dimensional structure with 100$\mu$m length, 25$\mu$m width, and 48 $\mu$m depth for a nanotechnology. The deep X-ray lithography is called as LIGA thchnology and getting a wide interest as a new technology for a nano-device. In this report all this works are summarized.

• The Korean Journal of Zoology
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• v.8 no.2
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• pp.33-36
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• 1965

We have carried out a study on the modification of the frequency of X-ray induced lethal and slow growing mutations by colchincine treatment before and after X-ray irradiation in Paramecium aurelia. 1. Lethal and slow-growing mutation induced by X-ray in Paramecium aurelia were reduced by colchicine treatment. 2. The effects of colchicine on the X-ray induced mutations were remarkable in the radiosensitive stages of cell division. 3. The pre-irradiation treatment with colchicine showed no significant influence on the frequency of mutations. 4. It is believed that the reduction of mutation induced by X-ray after treatment with colchicine was due to the fact that the delay of the cell division allowed more time for the pre-mutational damage to recover.

• Asian Pacific Journal of Cancer Prevention
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• v.15 no.22
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• pp.9759-9761
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• 2014

Purpose: To compare tumor size by mammography and sonography and align with pathological results in primary breast cancer cases. Materials and Methods: We retrospectively reviewed 95 primary breast cancer patients who underwent mammography and sonography from January 2011 to June 2012. The largest tumor diameter was chosen as sizing reference for each imaging modality. The measurements of mammography and sonography were considered concordant if they were within the measurement of pathological results ${\pm}0.5cm$. Pearson's correlation coefficient was calculated for imaging results. Results: The range of the maximum diameter was 0.6cm-10.5cm and mean value was $3.81{\pm}2.04cm$ by pathological results, 0.7cm-12.4 cm and $3.99{\pm}2.19cm$ by mammography, and 0.9cm-11.0cm and $3.63{\pm}2.01cm$ by sonography, respectively. Sonography (R: 0.754), underestimated tumor size, but had a better correlation with pathological tumor size compared to mammography (R: 0.676), which overestimated tumor size. Conclusions: Sonography is superior to mammography in assessment of primary breast cancer.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2004.04b
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• pp.77-80
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• 2004

In this study, the purpose is to verified the feasibility to develope Hybrid x-ray detector in order to resolve problems of direct and indirect x-ray detectors. The properties of X-ray detector depend on absorption of X-ray, charge generation by x-ray photon, leakage current. In this study, CdS was used as photoconductor, and $Y_2O_2S:Tb$ as x-ray phosphor was formed on CdS in order to embody Hybrid structure. And Screen printing was used to form Muli-layer. Characteristics of this specimen were analyzed by using SEM, and XRD. And Photoluminescence spectrum of $Y_2O_2S:Tb$, leakage current, with respect to applied voltages, output charge with respect to applied voltages, and X-ray sensitivity were measured. Also, linearity with respect to dose was measured. Leakage current was similar with direct digital x-ray detector, but sensitivity of the hybrid structure is much better than the single-layer structure.

• Journal of the Korean Society of Radiology
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• v.6 no.1
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• pp.39-45
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• 2012

Conventional periphery radiography system has a various problem such as patient dose and the pain of X-ray examination. In this paper, to solve these problems, we suggested insertional miniature x-ray system and we verified the feasibility of this system. First, we performed the Geant4 x-ray simulation to design x-ray collimator and filter to use miniature x-ray tube and we decided optimized thickness of filter and collimator. Also, we measured x-ray spectrum using CdTe detector and PX4 module to verify simulation results. Also, we acquired teeth image of fabricated phantom using conventional dental x-ray and prosed miniature x-ray system. As a results, our system has good image quality as compared to those of conventional systems. Our evaluation of the proposed system indicates that it can be potentially very useful for dental imaging.