• 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.

• Korean Journal of Veterinary Research
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• v.41 no.3
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• pp.333-342
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• 2001

To detect the genetic variations among infectious bursal disease (IBD) vaccine strains, the hypervariable region of VP2 gene of seven IBDV vaccine strains were amplified using reverse transcriptase/polymerase chain reation(RT/PCR). Ampllified PCR products of IBDV were cloned, sequenced, and compared with published sequences for IBDV. Vaccine strains (JOONG, HAN, B7, IB, BU2, G2, CIL) used in Korea and Korean field isolates (SH/92, K1, 310) had 81%(310 and HAN) ~ 98%(SH/92 and CIL) amino acid sequence similarity. Vaccine strains had 80%(HAN and IB) ~ 99%(JOONG and BU2) amino acid sequence similartiy. Intermediate plus vaccine strain, CIL was not substituted at positions 279(D $\rightarrow$ N) and 284(A $\rightarrow$ T), and conserved in serine-rich heptapeptide. At the two hydrophilic region, JOONG, IB and Bu2 strains had identical amino acid sequence comparing with STC strain. By phylogenetic analysis, JOONG and DAE strains were categorized in same group with BU2. The CIL and STC strains closely related but seperated from G2, HAN, B7 and IB strains.

• Journal of Korean Tunnelling and Underground Space Association
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• v.25 no.5
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• pp.373-386
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• 2023

To analyze the prediction of geological conditions and water-bearing zones, TSP was performed in the collapse zone of the fault zone. The results of the TSP were verified by comparing them to the face mapping results of the prediction zone. The rock quality prediction result of the TSP had an error of about 3 to 10 meters compared to the face mapping result, but the overall rock quality change and ground condition were analyzed to be relatively similar. In the water-bearing zones of the face mapping results, the Vp/Vs ratio ranges from 1.79 to 2.37 and the Poisson's ratio ranges from 0.27 to 0.39. In the sections other than the water-bearing zones, the Vp/Vs ratio ranges from 1.61 to 1.89, and the Poisson's ratio ranges from 0.19 to 0.3. As a result of analyzing the Vp/Vs ratio and Poisson's ratio in the water-bearing zones, it is analyzed that the sections with a Vp/Vs ratio of 2.0 or more and a Poisson's ratio of 0.3 or more have a high possibility of being water-bearing zones.

• Journal of Korean Academy of Oral and Maxillofacial Radiology
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• v.22 no.1
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• pp.87-94
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• 1992

The purpose of this study was to evaluate the effect of scatter radiation to dental x-ray film with long time-exposure in the different structures of the tooth, by using pinhole camera. For this study, pinhole camera, skull with tooth, and pocket dosimeter were used. The radiation with 70 and 90kVp and exposure time (minimum: 2.5 min., maximum 10 hrs.) was projected to the film in the pinhole camera. And density of the obtained x-ray film was measured with densitometer. In the intra-oral film taking, the amount of exposure of the scatter radiation affecting the thyroid gland area was measured with the dosimeter at the thyroid gland. The density of radiographs was compared in radiation projected with or without the metal cone of dental machine. The effect of the back scatter radiation to the film was also evaluated when the lead foil was removed. The obtained results were as follows: 1. A pinhole camera was a valuable device for locating the source of x-ray. 2. The scatter radiation affected the dental x-ray film when the radiation source was exposed. more than 5 hours'. In that case, the density of the scatter radiation could be observed visually. 3. The scatter radiation caused by short exposure of dental radiation didn't affect the diagnostic quality of the dental x-ray film. 4. The differences of densities between the tooth and the soft tissue according to exposure time showed 0.16 in 5 hours' exposure & 0.17 in 10 hours' exposure at 70 kVp & 0.12 in 5 hours' exposure & 0.13 in 10 hours' exposure at the 90kVp. 5. The differences of densities between the tooth and the soft tissue according to kVp showed no difference between 5 hours' exposure of tooth at 70 kVp and soft tissue at 90 kVp, but showed 0.05 high density in tooth when 10 hours' exposure at 90 kVp. 6. No difference of density was on radiographs taken with or without dental machine cone. 7. Back scatter radiation was recorded image of radiographs for only 3 min. 8. The amounts of the scatter radiation exposed to the thyroid gland in intraoral film taking were 1.12 mr in upper anterior, 0.55 mr in upper posterior, 2.75 mr in lower anterior, and 1.92 mr in lower posterior teeth.

• Journal of radiological science and technology
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• v.47 no.1
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• pp.1-6
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• 2024

In Recent years, there has been a noticeable increase in the global incidence of breast cancer, with approximately 2.3 million cases of female breast cancer reported worldwide in 2020. Numerous studies are currently underway to enhance the accuracy of breast cancer diagnosis through the development of digital mammography detectors. This study aims to create Monte Carlo simulation-based mammographic anti-scatter grids and investigate their utility in evaluating the performance of digital mammography detector. Two types of mammographic anti-scatter grids, MAM-CP and Senographe 600T HF, were created using Monte Carlo simulation software (MCNPX 2.7.0), with grid ratios of 3.7 : 1 and 5 : 1, respectively. The grid physical characteristics (sensitivity, exposure factor, contrast improvement ratio) were calculated based on the KS C IEC60627 in the simulations using two X-ray qualities, RQA-M2 (28 kVp) and MW4 (35 kVp). As the X-ray tube voltage increased from 28 kVp to 35 kVp, sensitivity and exposure factor exhibited a decreasing trend, while contrast improvement ratio demonstrated an increasing trend. With an increase in grid ratio from 3.7 : 1 to 5 : 1, all physical characteristics showed an upward trend. Our results were consistent with a previous study that conducted measurements of physical properties using a real phantom. However, the pattern of change in the contrast improvement ratio with X-ray tube voltage differed from the previous study.

• Journal of radiological science and technology
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• v.32 no.3
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• pp.299-306
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• 2009

Purpose : To compare radiation dose for coronary CT angiography (CTA) obtained with 6 examination protocols such as a retrospectively ECG gated helical scan, a prospectively ECG gated sequential scan, low kVp technique, and cardiac dose modulation technique. Materials and Methods : Coronary CTA was performed by using 6 current clinical protocols to evaluate effective dose and organ dose in primary beam area with anthropomorphic female phantom and glass dosimetric system in 64 channel multi-detector CT. After acquiring topograms of frontal and lateral projection with 80 kVp and 10 mA, main coronary scan was done with 0.35 sec tube rotation time, 40 mm collimation ($0.625\;mm{\times}64\;ea$), small scan field of view (32 cm diameter), 105 mm scan length. Heart beat rate of phantom was maintained 60 bpm in ECG gating. In constant mAs technique 120 kVp, 600 mA was used, and 100 kVp for low kVp technique. In a retrospectively ECG gated helical CT technique 0.22 pitch was used, peak mA (600 mA) was adopted in range of $40{\sim}80%$ of R-R interval and 120mA(80% reduction) in others with cardiac dose modulation. And 210 mAs was used without cardiac dose modulation. In a prospectively ECG gated sequential CT technique data were acquired at 75% R-R interval (middle diastolic phase in cardiac cycle), and 120 msec additional padding of the tube-on time was used. For effective dose calculation region specific conversion factor of dose length product in thorax was used, which was recommended by EUR 16262. Results : The mean effective dose for conventional coronary CTA without cardiac dose modulation in a retrospectively ECG gated helical scan was 17.8 mSv, and mean organ dose of heart was 103.8 mGy. With low kVp and cardiac dose modulation the mean effective dose showed 54.5% reduction, and heart dose showed 52.3% reduction, compared with that of conventional coronary CTA. And at the sequential scan(SnapShot pulse mode) under prospective ECG gating the mean effective dose was 4.9 mSv, this represents an 72.5% reduction compared with that of conventional coronary CTA. And heart dose was 33.8 mGy, this represents 67.4% reduction. In the sequential scan technique under prospective ECG gating with low kVp the mean effective dose was 3.0 mSv, this represents an 83.2% reduction compared with that of conventional coronary CTA. And heart dose was 17.7 mGy, this represents an 82.9% reduction. Conclusion : In coronary CTA at retrospectively ECG gated helical scan, cardiac dose modulation technique using low kVp reduced dose to 50% above compared with the conventional helical scan. And the prospectively ECG gated sequential scan offers substantially reduced dose compared with the traditional retrospectively ECG gated helical scan.

• Journal of the Korean Society of Radiology
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• v.17 no.4
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• pp.489-495
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• 2023

Radiation shielding facilities are constructed in locations where diagnostic radiation generators are installed, with the aim of preventing exposure for patients and radiation workers. The purpose of this study is seek to compare and validate the trend of attenuation thickness of lead, the primary material in these radiation shielding facilities, at different maximum tube voltages by Monte Carlo simulations and measurement. We employed the Monte Carlo N-Particle 6 simulation code. Within this simulation, we set a lead shielding arrangement, where the distance between the source and the lead sheet was set at 100 cm and the field of view was set at 10 × 10 cm². Additionally, we varied the tube voltages to encompass 80, 100, 120, and 140 kVp. We calculated energy spectra for each respective tube voltage and applied them in the simulations. Lead thicknesses corresponding to attenuation rates of 50, 70, 90, and 95% were determined for tube voltages of 80, 100, 120, and 140 kVp. For 80 kVp, the calculated thicknesses for these attenuation rates were 0.03, 0.08, 0.21, and 0.33 mm, respectively. For 100 kVp, the values were 0.05, 0.12, 0.30, and 0.50 mm. Similarly, for 120 kVp, they were 0.06, 0.14, 0.38, and 0.56 mm. Lastly, at 140 kVp, the corresponding thicknesses were 0.08, 0.16, 0.42, and 0.61 mm. Measurements were conducted to validate the calculated lead thicknesses. The radiation generator employed was the GE Healthcare Discovery XR 656, and the dosimeter used was the IBA MagicMax. The experimental results showed that at 80 kVp, the attenuation rates for different thicknesses were 43.56, 70.33, 89.85, and 93.05%, respectively. Similarly, at 100 kVp, the rates were 52.49, 72.26, 86.31, and 92.17%. For 120 kVp, the attenuation rates were 48.26, 71.18, 87.30, and 91.56%. Lastly, at 140 kVp, they were measured 50.45, 68.75, 89.95, and 91.65%. Upon comparing the simulation and experimental results, it was confirmed that the differences between the two values were within an average of approximately 3%. These research findings serve to validate the reliability of Monte Carlo simulations and could be employed as fundamental data for future radiation shielding facility construction.

• Journal of radiological science and technology
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• v.8 no.2
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• pp.3-9
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• 1985

From the study on the chest radiologic equipments and situations of university hospitals, general hospitals, and radiologic clinics located in Seoul area and Choong-cheong province, the author got conclusions as follows : 1. The rectfication methods of the equipments were employing mainly single or three-phase full wave, and 78% of the examined were using single phase full wave. 2. The focal sizes in case of small focus were less than 1.0mm in chest-only use, and more than 1.0mm in 81% of combined use. The focal sizes in case of large focus were more than 1.6mm in 78% of the total. 3. Maximum ratings of x-ray tubes were 47% at 125 kVp maximum tube voltage and 41% at 150kVp. The maximum tube currentes higher than 500mA were shown in 72% of all the examined. And the maximum exposure time was the range of 5-8sec. 4. Grid was not used in the 66% of all the hospitals. Equipment for chest-only was employing 10:1 grid ratio and the 2.0-2.9mmAl of total filtration formed 38% of all the examined. 5. In the processing time of exposed film, 68% of all was 90sec, and only 20% of all the examined used optimum developing temperature according to this condition. 6. In the radiographic conditions, more than 50% used low tube voltages lower than 70 kVp and only 3% of all the equipments used high tube voltages higher than 100 kVp. The 46.9% of all the equipments 300mA, and 53% of all used shorter exposure time less than 1/20(0.05) sec. 7. In the monthly average number of radiographs, 44% of all was x-ray the radiographs.

• Microbiology and Biotechnology Letters
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• v.49 no.1
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• pp.120-129
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• 2021

Rotavirus A (RVA) is recognized as a major etiology responsible for the development of acute gastroenteritis in children worldwide. The purpose of the present study was to perform the molecular characterization of RVA. A total of 323 stool specimens collected from hospitalized children with acute gastroenteritis in Chiang Rai, Thailand, in 2016-2018 were identified for G- and P-genotypes through RT-PCR analysis. RVA was more prevalent in 2017-2018 (37.8%) than in 2016-2017 (23.2%). The seasonal peak of RVA occurred from March to April. G3P[8] was predominant in 2016-2017 (90.6%) and 2017-2018 (58.6%). Other genotypes including G1P[8], G8P[8], G9P[8], and mixed infections were also identified. G3P[8] strains clustered together in the same lineage with other novel human equine-like G3P[8] strains previously identified in multiple countries and presented a genotype 2 constellation (G3-P[8]-I2-R2-C2-M2-A2-N2-T2-E2-H2). Several amino acid differences were observed in the antigenic epitopes of the VP7 and VP8* capsid proteins of the equine-like G3P[8] compared with those of the RVA vaccine strains. The homology modeling of the VP7 and VP8* capsid proteins of the equine-like G3P[8] strains evidently exhibited that these residue differences were present on the surface-exposed area of the capsid structure. The emergence of the equine-like G3P[8] strains in Thailand indicates the rapid spread of strains with human and animal gene segments. Continuous surveillance for RVA is essential to monitor genotypes and genetic diversity, which will provide useful information for selecting rotavirus strains to develop a safe and effective RVA vaccine that is efficacious against multiple genotypes and variants.

• 한국지구물리탐사학회:학술대회논문집
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• 2007.12a
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• pp.43-51
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• 2007

In order to investigate the velocity structure of the southern part of the Korean peninsula, exploded seismic signals were recorded for 120 s along a 294-km WNW-ESE line and 150 s along a 335-km NNW-SSE line in 2002 and 2004, respectively. Velocity tomograms were derived from inverting P-wave and S-wave first arrival times. The raypaths indicate several midcrust interfaces. The shallowest one is at the approximate depth of $2{\sim}3\;km$ with refraction velocities of approximately Vp=6.0 and Vs=3.5 km/s, respectively. The second one of $15{\sim}17\;km$ depth has refraction velocities of approximately Vp=7.1 and Vs=3.7 km/s, respectively. The deepest significant interface varies in depth from 30.8 km to 36.1 km. The critically refracting Vp of $7.8{\sim}8.1\;km/s$ and Vs of $4.2{\sim}4.6\;km/s$ along this interface which may correspond to the Moho discontinuity. The velocity tomograms show (1) existence of a low-velocity zone centered at $6{\sim}7\;km$ depth under the Okchon fold belt and the Yeongnam massif, (2) extension of the Yeongdon fault down to greater than 10 km, and (3) existence of high-velocity materials under the Gyeongsan basin less than 4.2 km thick.