• Journal of the Korean Society of Radiology
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• v.5 no.2
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• pp.93-96
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• 2011

Currently, the development of direct conversion radiation detector using photoconductor materials is progressing in widely. Among of theses photoconductor materials, mercuric iodide compound than amorphous selenium has excellent absorption and sensitivity of high energy radiation. Also, the detection efficiency of signal generated in photoconductor film varies by electric filed and geometric distribution according to top-bottom electrode size. Therefore, in this work, the x-ray detection characteristics are investigated about the size of top electrode in $HgI_2$ photoconductor film. For sample fabrication, to solve the problem that is difficult to make a large area film, we used the spatial paste screen-print method. And the sample thickness is $150{\mu}m$ and an film area size is $3cm{\times}3cm$ on ITO-coated glass substrate. ITO(Indium-Tin-Oxide) electrode was used as top electrode using a magnetron sputtering system and each area is $3cm{\times}3cm$, $2cm{\times}2cm$ and $1cm{\times}1cm$. From experimental measurement, the dark current, sensitivity and SNR of the $HgI_2$ film are obtained from I-V test. From the experimental results, it shows that the sensitivity increases in accordance with the area of the electrode but the SNR is decreased because of the high dark current. Therefore, the optimized size of electrode is importance for the development of photoconductor based x-ray imaging detector.

• Journal of radiological science and technology
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• v.40 no.3
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• pp.461-468
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• 2017

This study measured and compared the protective clothing using Pb used for shielding in a diagnostic X-ray energy range, and the shielding rates of X-ray fusion shielding materials using Si and $TiO_2$. For the experiment, a pad type shielding with a thickness of 1 mm was prepared by mixing $Si-TiO_2$, and the X-ray shielding rate was compared with 0.5 mmPb plate of The shielding rate of shielding of 0.5 mmPb plate 95.92%, 85.26 % based on the case of no shielding under each 60 kVp, 100 kVp tube voltage condition. When the shielding of $Si-TiO_2$ pad was applied, the shielding rate equal to or greater than 0.5 mmPb plate was obtained at a thickness of 11 mm or more, and the shielding rate of 100% or more was confirmed at a thickness of 13 mm in 60 kVp condition. When the shielding of $Si-TiO_2$ pad was applied, the shielding rate equal to or greater than 0.5 mmPb plate was obtained at a thickness of 17 mm or more, and a shielding rate of 0.5 mmPb plate was observed at a thickness of 23 mm in 100 kVp condition. Through the results of this study, We could confirm the possibility of manufacturing radiation protective materials that does not contain lead hazard using various metalic compound and liquid Si. This study shows that possibility of liquid Si and other metalic compound can harmonize easily. Beside, It is flexible and strong to physical stress than Pb obtained radiation protective closthes. But additional studies are needed to increase the shielding rate and reduce the weight.

• Journal of the Korean Institute of Traditional Landscape Architecture
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• v.28 no.2
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• pp.109-117
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• 2010

This study conducts a case analysis based on the Olympic Forest Park in Beijing, which is specially designed for the 2008 Beijing Olympic Games. The construction of the Olympic Forest Park not only comprises the design philosophy of city parks and forest parks, but also applies Chinese traditional design elements. This study, first, researches on the design concepts of city parks in the context of traditional landscape architecture elements from both physical and cultural perspectives. The author studies the related materials including the"General Introduction of the Beijing Olympic Forest Park Landscape Plan", and employs the approaches of site investigation and user survey and interview, to analyze the cognition and preference degree of the various traditional design elements displayed in the Olympic Forest Park. To quantize the survey data on the Olympic Forest Park, this study uses the spss(v17.0) software to run a frequency analysis and presents detailed demographic, frequencies and means analyses. The author then reaches the conclusion on the preference degree of the various Chinese traditional design elements in the Olympic Forest Park. According to the analysis result, the elements that appear with the highest frequencies are mountains and waters, traditional garden plants and artistic conception. The most favorable elements are in sequence traditional garden architecture, traditional garden philosophical thinking and artistic conception. The Olympic Forest Park in Beijing is constructed on the basis of multiple design elements, comprising Chinese traditional design elements and the historical axis. As an exemplification of contemporary city park that reflects the variation of age and development of society, the Olympic Forest Park offers the reference for the selection of traditional design elements in the future schemes of city parks. However, due to the difficulty in gathering materials about the Forest Park and the limitations on the location and time constrain of the survey, there exists lack of sufficiency that could be improved in the future.

• Korean Journal of Dental Materials
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• v.45 no.4
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• pp.233-242
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• 2018

The purpose of this study is to evaluate the effect of resin cement color on the color of commercially available zirconia crown. The zirconia and resin cements used for the experiment were $NuSmile^{(R)}$ ZR Zirconia LT Shade (LT), $RelyX^{TM}$ U200 TR, A2, and A3O (TR, A2, A3O). The disks of zirconia and resin cements with diameters of 5 mm and thicknesses of 1 mm were prepared. Five disks were made for each specimen. The CIE $L^*a^*b^*$ values of zirconia, resin cements and the combinations thereof were measured on black and white backgrounds, respectively, using a spectrophotometer. The color effect of resin cement on the color of the zirconia crown was evaluated by calculating translucency parameter (TP), contrast ratio (CR), and color differences (${\Delta}E{^*}_{ab}$) based on the measured CIE $L^*a^*b^*$ values. The statistical significances were verified by one-way ANOVA and the Tukey-multiple comparisons tests. As a result, the TP and CR values were decreased (p<0.05) and increased, respectively, in the combination of zirconia and resin cement disks compared to zirconia disk per se. When using the black background, the ${\Delta}E{^*}_{ab}$ values between zirconia and the combination of the zirconia and three resin cement disks were imperceptible level. The A3O showed the lowest ${\Delta}E{^*}_{ab}$ value among three resin cements. When using the white background, the ${\Delta}E{^*}_{ab}$ values between zirconia and the combination of zirconia and TR resin cement (LT/TR) disks showed acceptable level. However, the ${\Delta}E{^*}_{ab}$ values between zirconia and the combination of zirconia and A2 resin cement (LT/A2) disks showed unacceptable level. Meanwhile, the ${\Delta}E{^*}_{ab}$ values between zirconia and the combination of zirconia and A3O resin cement (LT/A3O) disks showed perceptible but acceptable level. Within the limits of this study, the colors of resin cements did not cause unacceptable color changes of zirconia except the combination of LT/A2 on the white background. The resin cement that gave the least color changes to zirconia was A3O. This means that the resin cement A3O is recommended to use for minimizing color changes when cementing commercially available zirconia crown to tooth.

• Journal of Radiation Protection and Research
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• v.40 no.1
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• pp.1-9
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• 2015

Compton cameras overcome several limitations of conventional mechanical collimation based gamma imaging devices, such as pin-hole imaging devices, due to its electronic collimation based on coincidence logic. Especially large-scale Compton camera has wide field of view and high imaging sensitivity. Those merits suggest that a large-scale Compton camera might be applicable to monitoring nuclear materials in large facilities without necessity of portability. To that end, our research group have made an effort to design a large-scale Compton camera for safeguard application. Energy resolution or position resolution of large-area detectors vary with configuration style of the detectors. Those performances directly affect the image quality of the large-scale Compton camera. In the present study, a series of Geant4 Monte Carlo simulations were performed in order to examine the effect of those detector parameters. Performance of the designed large-scale Compton camera was also estimated for various monitoring condition with realistic modeling. The conclusion of the present study indicates that the energy resolution of the component detector is the limiting factor of imaging resolution rather than the position resolution. Also, the designed large-scale Compton camera provides the 16.3 cm image resolution in full width at half maximum (angular resolution: $9.26^{\circ}$) for the depleted uranium source considered in this study located at the 1 m from the system when the component detectors have 10% energy resolution and 7 mm position resolution.

• Economic and Environmental Geology
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• v.6 no.1
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• pp.29-64
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• 1973

A land resources survey in the semi-arid area, Mula in S. E. Spain, of $400km^2$ is compiled. The basic aim of the project is to investigate the intrinsic qualities of the land resources of the area by means of applying an integrated method of natural resources survey mainly concerning with analysis and synthesis of land complexes, each of them represents an area or a group of areas with similar patterns of landforms, soils and vegetation, based on a geomorphological approach. The area is characterized by a linear arrangement of relief pattern with an asymmetric homoclinal repetition of slope attitudes elongating WSW-ENE, dipping steeply on the NW sides and gently on the SE sides, which have been resulted from the post-Alpine folding of the Triassic to Cretaceous limestone, the Eocene limestone, the Oligocene sandstone and the lower Miocene limestone and marl, and the post-lower Miocene faulting, tilting and subsequent differential erosion of the Miocene sedimentary formations. An integrated body of information in geology, landforms, soils and vegetation, which are significantry interrelated as an environmental complex, has been obtained. Using this data, 26 land complexes developing on the various situations of landforms, such as folded mountain ranges, tilted tablelands, bevelled cuestas, degraded hill-lands associating with enormous foots lopes, undulating terrains and terraced or flat plains, have been differentiated, mapped and described. The soils of the area are mostly light colored calcic lithosols which have been derived dominantly from the marly parent materials and developed into remarkable slope catenas in some places depending on the relief conditions. The land uses of the area are mainly characterized by the perennially irrigated cultivation of citrus orchards along the terraced alluvial deposits fringing the Segura and Mula River, and the dry-land cereal cultivation on gentler slopes. Pioneer dry-land cultivations within the shrubs on steeper slopes are restricted to the unchannelled tributary drainage floors. The availability of water is a fundamental controlling factor for existence of native and cultivated vegetation as a whole, and a number of active processes including sheet wash and gully erosion, especially on the scarp slopes, are the other important factors to be considered in conservation and management of the land in the area.

• Radiation Oncology Journal
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• v.19 no.2
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• pp.163-170
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• 2001

Purpose : The measurement of radiation survival using a clonogenic assay, the established standard, can be difficult and time consuming. In this study, We have used the MTT assay, based on the reduction of a tetrazolium salt to a purple formazan precipitate by living cells, as a substitution for clonogenic assay and have examined the optimal condition for performing this assay in determination of radiation sensitivity. Materials and Methods : Four human cancer cell lines - PCI-1, SNU-1066, NCI-H630 and RKO cells have been used. For each cell line, a clonogenic assay and a MTT assay using Premix WST-1 solution, which is one of the tetrazolium salts and does not require washing or solubilization of the precipitate were carried out after irradiation of 0, 2, 4, 6, 8, 10 Gy. For clonogenic assay, cells in $25\;cm^2$ flasks were irradiated after overnight incubation and the resultant colonies containing more than 50 cells were scored after culturing the cells for $10\~14$ days. For MTT assay, the relationship between absorbance and cell number, optimal seeding cell number, and optimal timing of assay was determined. Then, MTT assay was performed when the irradiated cells had regained exponential growth or when the non-irradiated cells had undergone four or more doubling times. Results : There was minimal variation in the values gained from these two methods with the standard deviation generally less than $5\%$, and there were no statistically significant differences between two methods according to t-test in low radiation dose (below 6 Gy). The regression analyses showed high linear correlation with the $R^2$ value of $0.975\~0.992$ between data from the two different methods. The optimal cell numbers for MTT assay were found to be dependent on plating efficiency of used cell line. Less than 300 cells/well were appropriate for cells with high plating efficiency (more than $30\%$). For cells with low plating efficiency (less than $30\%$), 500 cells/well or more were appropriate for assay. The optimal time for MTT assay was after 6 doubling times for the results compatible with those of clonogenic assay, at least after 4 doubling times was required for valid results. In consideration of practical limits of assay (12 days, in this study) cells with doubling time more than 3 days were inappropriate for application. Conclusion : In conclusion, it is found that MTT assay can successfully replace clonogenic assay of tested cancer cell lines after irradiation only if MTT assay was undertaken with optimal assay conditions that included plating efficiency of each cell line and doubling time at least.

• The Korean Journal of Nuclear Medicine Technology
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• v.13 no.3
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• pp.61-66
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• 2009

Purpose: Glomerular filtration rate (GFR) is considered as the best overall index for the level of renal function, diagnosis of doubtful kidney disease, progress observation from chronic kidney disease and is measured with the various methods. In this study, We measured standard GFR by Gates method and attempted to compare the result with serum creatinin-based, Cockcroft-Gault(C-G) formula and Modification of Diet in Renal Disease (MDRD) formula. Materials and methods: 217 patients (127 men, 90 women, mean age $51.3{\pm}16.9$) with various renal function were examined. we compared the GFR using $^{99m}Tc$-DTPA (Gates), C-G formula and MDRD formula. Results: Significant correlations were noted between 2 different GFR estimates (from C-G formula: r=0.864, p<0.0001, MDRD formula: r=0.831, p<0.0001) and $^{99m}Tc$-DTPA (Gates) GFR. Average of serum creatinine (Scr) was measured with $3.0{\pm}3.1\;mg/dL$, In patients with normal renal function (Scr<1.5 mg/dL), $^{99m}Tc$-DTPA (Gates) GFR was statistically significant to C-G formula (p<0.0001) and MDRD formula (p<0.0001). In patients with mild to moderate renal insufficiency (1.5$^{99m}Tc$-DTPA (Gates) GFR was not statistically significant to C-G formula (p=0.181) and MDRD formula (p=0.127). In patients with severe renal insufficiency (Scr>4.0mg/dL), $^{99m}Tc$-DTPA (Gates) GFR was statistically significant to C-G formula and MDRD formula (p<0.0001). Conclusions: Glomerular filtration rate using Gates method was closly correlated to C-G formula and MDRD formula. In patients with normal renal function, $^{99m}Tc$-DTPA (Gates) GFR was significantly lower than C-G formula and MDRD formula. In patients with mild to moderate renal insufficiency, $^{99m}Tc$-DTPA (Gates) GFR was simmilar with C-G formula and MDRD formula. In patients with severe renal insufficiency, $^{99m}Tc$-DTPA (Gates) GFR was significantly higher than C-G formula and MDRD formula. None of the three different methods was clearly superior to the others.

• The Korean Journal of Nuclear Medicine Technology
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• v.13 no.3
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• pp.137-142
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• 2009

Purpose: World Health Organization (WHO) have suggested that an individual's 10-year absolute fracture risk is more reliable than Bone Mineral Density (BMD) measurement as the predictor of osteoporotic fracture. In 2008, Fracture Risk Assessment Tool ($FRAX^{TM}$) was developed by WHO to evaluate fracture risk of patients based on individual's clinical risk factors. The purpose of this study is to offer the comparative analysis of the existing GE prodigy and $FRAX^{TM}$ Tool in Absolute Fracture Risk Assessment Tool. Materials and Methods: 201 women ($55{\pm}3.5$ years) underwent femoral neck BMD measurement using GE Prodigy. The 10-year probability (%) of hip fracture (or a major osteoporosis-related fracture) was estimated using T-scores of GE prodigy and $FRAX^{TM}$. We made a comparative analysis of these data using SPSS (Ver.12). Results: There was a significant difference statistically between T-score ($-0.52{\pm}0.97$) of GE prodigy and T-score ($-1.45{\pm}0.81$) of $FRAX^{TM}$ (r=0.977, p=0.000). Also, there was a significant difference statistically between a major osteoporosis- related fracture ($9.15{\pm}3.71$) of GE prodigy and a major osteoporosis-related fracture ($4.87{\pm}1.51$) of $FRAX^{TM}$ (r=0.909, p=0.000). Moreover, a statistically significant difference was found in the 10-year probability of hip fracture of GE prodigy ($1.56{\pm}1.48$) and of hip fracture ($0.53{\pm}0.61$) of $FRAX^{TM}$ (r=0.905, p=0.000). Conclusions: There was a significant difference statistically between GE prodigy and $FRAX^{TM}$ Tool in Absolute Fracture Risk Assessment Tool. Especially, T-score, a major osteoporosis-related fracture and the 10-year probability of hip fracture that were estimated using GE prodigy tended to show the higher results than one evaluated by $FRAX^{TM}$ Tool. In conclusion, $FRAX^{TM}$ Tool may provide a better tool. The application of $FRAX^{TM}$ Tool as a fracture predictor remains to be clarified.

• Investigative Magnetic Resonance Imaging
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• v.10 no.2
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• pp.98-107
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• 2006

Magnetization Transfer (MT) imaging generates contrast dependent on the phenomenon of magnetization exchange between free water proton and restricted proton in macromolecules. In biological materials in knee, MT or cross-relaxation is commonly modeled using two spin pools identified by their different T2 relaxation times. Two models for cross-relaxation emphasize the role of proton chemical exchange between protons of water and exchangeable protons on macromolecules, as well as through dipole-dipole interaction between the water and macromolecule protons. The most essential tool in medical image manipulation is the ability to adjust the contrast and intensity. Thus, it is desirable to adjust the contrast and intensity of an image interactively in the real time. The proton density (PD) and T2-weighted SE MR images allow the depiction of knee structures and can demonstrate defects and gross morphologic changes. The PD- and T2-weighted images also show the cartilage internal pathology due to the more intermediate signal of the knee joint in these sequences. Suppression of fat extends the dynamic range of tissue contrast, removes chemical shift artifacts, and decreases motion-related ghost artifacts. Like fat saturation, phase sensitive methods are also based on the difference in precession frequencies of water and fat. In this study, phase sensitive methods look at the phase difference that is accumulated in time as a result of Larmor frequency differences rather than using this difference directly. Although how MT work was given with clinical evidence that leads to quantitative model for MT in tissues, the mathematical formalism used to describe the MT effect applies to explaining to evaluate knee disorder, such as anterior cruciate ligament (ACL) tear and meniscal tear. Calculation of the effect of the effect of the MT saturation is given in the magnetization transfer ratio (MTR) which is a quantitative measure of the relative decrease in signal intensity due to the MT pulse.