• The Journal of Korean Society for Radiation Therapy
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• v.33
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• pp.25-33
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• 2021

Purpose : The purpose of this study is to evaluate the accuracy and usefulness of the Trigger mode for the Respiratory Gated Radiation Therapy (RGRT) Materials and methods : A QUASAR respiratory phantom that inserted a 3 mm fiducial marker (a gold marker) was used to estimate the accuracy of the Trigger mode. And the 20 bpm was used as reference respiration rate in this study. The marker that placed at the center of the phantom was contoured, and the lower threshold of a gating window was fixed at 2.0 mm using an OBI with Truebeam STx^TM. The upper threshold was measured every 0.5 mm from 1.0 mm to 3.0 mm. The respiration rates were changed every 10 bpm from 10 bpm to 60 bpm. We repeatedly measured five times to check the error rate of the trigger mode in the same condition. Result : The differences of a distance from a peak phase to upper threshold, 1.0 to 3.0 mm at a 20 bpm as a reference for 3 days in a row were 0.68±0.05 mm, 0.91±0.03 mm, 1.23±0.03 mm, 1.42±0.04 mm, and 1.66±0.06 mm, respectively. Measurement result of changes in respiratory rate compared to baseline respiratory rate in maximum absolute difference. The coefficient of determination (R2) to estimate the correlation between the respiration velocity and variation of absolute difference was on average 0.838, 0.887, 0.770, 0.850, and 0.906. The p-values of all the variables were below 0.05. Conclusion : Using Trigger mode during respiratory gated radiation therapy (RGRT), accuracy and usefulness of trigger mode at reference breathing rate were confirmed. However, inaccuracies depending on the rate of breathing it could be uncertain in case of respiration rate is faster than 20 bpm as a standard respiration rate compared to slower than 20 bpm. Consequently, when conducting a RGRT using the trigger mode, real time monitoring is required with well educated respiration.

• Journal of the Korean Society of Radiology
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• v.82 no.6
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• pp.1505-1523
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• 2021

Purpose Although chest CT has been discussed as a first-line test for coronavirus disease 2019 (COVID-19), little research has explored the implications of CT exposure in the population. To review chest CT protocols and radiation doses in COVID-19 publications and explore the number needed to diagnose (NND) and the number needed to predict (NNP) if CT is used as a first-line test. Materials and Methods We searched nine highly cited radiology journals to identify studies discussing the CT-based diagnosis of COVID-19 pneumonia. Study-level information on the CT protocol and radiation dose was collected, and the doses were compared with each national diagnostic reference level (DRL). The NND and NNP, which depends on the test positive rate (TPR), were calculated, given a CT sensitivity of 94% (95% confidence interval [CI]: 91%-96%) and specificity of 37% (95% CI: 26%-50%), and applied to the early outbreak in Wuhan, New York, and Italy. Results From 86 studies, the CT protocol and radiation dose were reported in 81 (94.2%) and 17 studies (19.8%), respectively. Low-dose chest CT was used more than twice as often as standard-dose chest CT (39.5% vs.18.6%), while the remaining studies (44.2%) did not provide relevant information. The radiation doses were lower than the national DRLs in 15 of the 17 studies (88.2%) that reported doses. The NND was 3.2 scans (95% CI: 2.2-6.0). The NNPs at TPRs of 50%, 25%, 10%, and 5% were 2.2, 3.6, 8.0, 15.5 scans, respectively. In Wuhan, 35418 (TPR, 58%; 95% CI: 27710-56755) to 44840 (TPR, 38%; 95% CI: 35161-68164) individuals were estimated to have undergone CT examinations to diagnose 17365 patients. During the early surge in New York and Italy, daily NNDs changed up to 5.4 and 10.9 times, respectively, within 10 weeks. Conclusion Low-dose CT protocols were described in less than half of COVID-19 publications, and radiation doses were frequently lacking. The number of populations involved in a first-line diagnostic CT test could vary dynamically according to daily TPR; therefore, caution is required in future planning.

• The Journal of Korean Society for Radiation Therapy
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• v.23 no.1
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• pp.41-49
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• 2011

Purpose: This study is designed to investigate radiotherapic valuation of Paraffin Wax, which is newly formed for this study and generally utilized in dentistry, and Mouth Piece and Putty impression, which are commonly used in radiotherapy, for oral cavity as a compensator. Materials and Methods: Each compensator was formed by $10{\times}10{\times}1cm$ and measured radiation dose attenuation ratio with reference of water phantom which is made of tissue-equivalent materials. Two patients with oral cancer underwent DRR (Digitally Reconstructed Radiogrph) of Offline Review Program of Aria System and Portal vision for 5 times for each material to evaluate reproducibility by each filling materials. Moreover, MU (monitor unit) changes by dose absorption were considered in the case of inevitable implication of an filling materials in the range for radiotherapy. Results: Radiation dose attenuation ratios were shown -0.7~+3.7% for Mouth Piece, +0.21~+0.39% for Paraffin Wax and -2.71~-1.76% for Putty impression. Error ranges of reproducibility of positions were measured ${\pm}3mm$ for Mouth Piece, ${\pm}2mm$ for Paraffin Wax and ${\pm}2mm$ mm for Putty impression. Difference of prescription MU from dose absorption with an filling material increased +7.8% (250 MU) in Putty impression and -0.9% (230 MU) in Paraffin Wax as converted into a percentage from the standard phantom, Water 232 MU. Conclusion: Dose reduction of boundary between cavity and tissue was observed for Mouth Piece. Mouth Piece also had low reproducibility of positions as it had no reflection of anatomy of oral cavity even though it was a proper material to separate Maxilla and Mandible during therapy. On the other hand, Putty impression was a suitable material to correctly re-position oral cavity as before. However, it risked normal tissues getting unnecessary over irradiation and it caused radiation dose decrease by -2.5% for 1cm volume in comparison of it of water phantom. Dose reduction in Paraffin Wax, Fat Tissue-Equivalent Material, was smaller than other impressions and position reproducibility of it was remarkable as it was possible to make an anatomy reflected impression. It was also well fitted to oral cavity to transfer radiation dose planned in radiotherapy. Thus, Paraffin Wax will be an ideal material in radiotherapy for patients with oral cancer.

• Analytical Science and Technology
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• v.26 no.3
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• pp.165-173
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• 2013

To establishment of PT Program for Indoor air quality field that manufacture of confidential development PTMs (proficiency testing materials) and examined of proficiency testing evaluation included sampling process whether or not that is valid. Confirmation of homogeneity and stability of PTMs prepared. PTMs were confirmed to be homogeneous enough to be used as proficiency testing materials since withinbottle homogeneities of the RMs were lower than 0.3 times of targeted standard deviation of proficiency testing. The result of this study showed that the Robust RSD of proficiency testing for VOCs (volatile organic compounds) appeared 23~43% in concentration of 50~320 ${\mu}g/m^3$ for Method A(Distribution by adsorption in Tenax-tube of VOCs), but less 13~42% in concentration of 200~1200 ${\mu}g/m^3$, 16~31% in concentration of 100~450 ${\mu}g/m^3$ for Method B (distribution by VOCs of gas phase in 10L Tedalr bag), C (directly sampling of cylinder with high pressure) respectively. The result of this study showed that method C with sampling is most adequate to the proficiency testing for VOCs in indoor air.

• Korean Journal of Environmental Biology
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• v.23 no.3 s.59
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• pp.293-303
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• 2005

Japanese medaka, Oryzias latipes is widely distributed in the North East Asia including Korea, Japan and east China, and commonly used for freshwater toxicity tests and cytotoxicological studies worldwide. In this study, a series of experiments were conducted to identify the potential of the fish as a standard test species for saltwater toxicity evaluation such as marine receiving waters, ocean-dumped materials and sediment pore waters etc. Hatching, growth and mortality rates of the fish were estimated with the wide ranges of salinity from freshwater to seawater (35 psu). Direct exposure of the fertilized eggs in freshwater to the wide ranges of salinity (from 0 to 35 psu) without pre- acclimation to the saltwater revealed no significant differences in hatching rates by salinities (p =0.24). On the other hand, medaka larvae hatched in freshwater and exposed to saltwater directly showed high mortality at > 25 psu treatment groups (p < 0.0001). However, there was no significant difference in mortality of medaka larvae hatched in 13.8 and 14.2 psu at the wide ranges of salinities ($0\~35$ psu). Growth rates of medaka larvae hatched in the above two salinities showed no differences in body length either from 0 to 35 psu treatment groups (p =0.64 for 13.8 psu group and p=0.32 for 14.2 psu group). The number of gill chloride cell in medaka larvae sharply increased when the larvae were exposed to high salinity. Reference tests with zinc chloride revealed 96h $LC_{50}=8.84(7.19\~10.87)mg\;L^{-1}$ using 7~10 day old medaka larvae. These were comparable or better sensitivity in comparison with the other standard test species such as North American sheepshead minnow Cyprinodon variegatus. Based on the results of these experiments, hatching rates and larvalmortality of medaka must be good toxicity parameters for seawater bioassay and the species seems to be a good standard species for both the freshwater and seawater toxicity test.

• Journal of the Society of Disaster Information
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• v.18 no.1
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• pp.182-193
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• 2022

Purpose: By measuring and evaluating the risk of biodiesel through non-volatile residue (NVR) and flash point and explosion limit measurement at a specific temperature according to ASTM test standards, the risk of chemical fire causative substances is identified and a universal evaluation method By derivation and securing the risk-related data of the material, it can be used for the identification and analysis of the cause of the fire, and it can be applied to the risk assessment of other chemical substances Method: In order to measure the risk of biodiesel, it was measured using the non-volatile residue(NVR) measurement method, which measures how much flammable liquid is generated at a specific temperature. Heating was tested by applying KS M 5000: 2009 Test Method 4111. In addition, the flash point was measured using the method specified in ASTM E659-782005, and the energy supply method was measured using the constant temperature method. In addition, the explosion limit measurement was conducted in accordance with ASTM E 681-04 「Standard test method for concentration limits of flammability of chemicals(Vapors and gases)」 test standard. Result: As a result of checking the amount of combustible liquid by the non-volatile residue (NVR)measurement method, the non-volatile residue(NVR) of general diesel when left at 105±2℃ for 3 hours was about 30% (70% of volatile matter) and about 4% of biodiesel. In addition, similar results were obtained for the non-volatile residue(NVR)heating temperature of 150±2℃, 3 hours and 200±2℃ for 1 hour, and white smoke was generated at 200℃ or higher. In addition, similar values were obtained as a result of experimentally checking the explosion (combustion) limits of general diesel, general diesel containing 20% biodiesel, and 100% biodiesel. Therefore, it was confirmed that the flammability risk did not significantly affect the explosion risk. Conclusion: The results of this study suggested the risk judgment criteria for mixtures through experimental research on flammable mixtures for the purpose of securing the effectiveness, reliability, and reproducibility of the details of the criteria for determining dangerous substances in the existing Dangerous Materials Safety Management Act. It will be possible to provide reference data for the judgment criteria for flammable liquids that are regulated in the field. In addition, if the know-how for each test method is accumulated through this study, it is expected that it will be used as basic data in the research on risk assessment of dangerous substances and as a basis for research on the determination of dangerous substances.

• Journal of Korean Ophthalmic Optics Society
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• v.18 no.1
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• pp.1-10
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• 2013

Purpose: This study is conducted to evaluate the job stressors for opticians in Ulsan city. Methods: We investigated job stress of 180 opticians working in Ulsan. The results of this study from The Korean standard job stressors assessment tool developed by Korea occupational safety and health agency (KOSHA) was compared with Korean reference value. The questionnaire on the social, demographic characteristics of opticians was also used to find the factors affecting to job stressors by using multiple linear regression analysis. Results: Among the eight fields of stressors, the interpersonal conflict (the median value; 33.4, the measurements; men; 38.8, women; 41.5) and company culture (the median; 41.7, the measurements; men; 47.4, women; 49.3) were higher than the median value of the Korean workers. By multiple linear regression analysis, the significant factors to the interpersonal conflict were the duty, working hours, unmarried, average salary. In terms of the company culture, last school, rest day of month, job career, average salary and working hours were significantly associated to the score of company culture. Conclusions: Based on the results, important factor in the formation of a positive organizational culture through to improve treatment of opticians investigation and mutual horizontal communication systems in the workplace for the manage on interpersonal conflict and company culture.

• Journal of Soil and Groundwater Environment
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• v.17 no.6
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• pp.33-42
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• 2012

This study was performed to find the problems according to interference factors (organic matter, pH, Cr, Mn, Fe, clay, and etc.) when we analyzed the hexavalent chromium [Cr(VI)] in soils using UV/VIS spectrometer (US EPA 7196A), attempted to evaluate the domestic applicability of analytical method (US EPA 7199) using IC-UV/VIS spectrometer as alternative method. The recovery rate of certified reference materials was 75.0% (US EPA 7196A) and 101.4% (US EPA 7199) by the analytical methods. As the results of performing QA/QC about US EPA 7199, method detection limit (MDL) and limit of quantification (LOQ) were 0.062 mg/kg, 0.196 mg/kg, respectively. The LOQ of US EPA 7199 was lower than that of the current soil official testing method in Korea (0.5 mg/kg). Cr(VI) contents in 23 soil samples were compared by the analytical methods of EPA 7196A and 7199. Cr(VI) was detected in 13 of 23 soil samples by EPA 7196A, while EPA 7199 was not detected in any soil samples. The Cr(VI) content in 23 soil samples by EPA 7196A was not clearly correlated with Cr, Fe, Mn and clay content in the soil samples. However, the contents of Cr(VI) and organic matter of the soil samples had the highest coefficient of determination ($R^2$) of 0.80. In order to evaluate the correlation between the recovery rates of Cr(VI) and organic matter contents in the soil samples, the recovery rates of 5 soil samples added Cr(VI) standard solution were analyzed by the analytical methods. According to the results, the higher the organic matter contents in soil samples, the lower the recovery rates of Cr(VI) by US EPA 7196, while in case of US EPA 7199, the recovery rates were stable regardless of the organic matter contents.

• Journal of Nuclear Fuel Cycle and Waste Technology(JNFCWT)
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• v.2 no.2
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• pp.97-104
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• 2004

Neutron induced prompt gamma-ray spectroscopy(NIPS) system measures the prompt gamma-ray emitting by the interaction of a neutron with various materials. This system will be of great benefit to scientists worldwide, since it provides the non-destructive measurement of many element in either solid or liquid wastes. In this study, the full-energy-peak (FEP) efficiency calibration for a HPGe detector was constructed in the ${\gamma}$-ray energy range from 80 keV to 8 MeV, using $^{l33}$Ba and >TEX>$^{152}Eu$ RI sources and $ ^{35}Cl(n, ${\gamma}$)^{36}Cl$ thermal neutron captured reaction. The FEP efficiency curve for the higher energies using the $^{35}Cl(n, ${\gamma}$)^{36}Cl$ reaction was normalized with the curve obtained from the RI sources, since the accurate activity of its prompt ${\gamma}$-ray is unknown. The average thermal neutron flux was theoretically calculated using the FEP efficiency curve for the KCl standard solutions. The NIPS system equipped with a ${\gamma}$-${\gamma}$ coincidence setup with two n-type coaxial HPGe detectors was considered in order to reduce the interfering ${\gamma}$-ray background. The FEP efficiency curve for the ${\gamma}$-${\gamma}$ coincidence system was also obtained for full energy range. The performance of the normal and coincidence NIPS system was tested by comparing signal-to-noise ratio in each mode using the reference sample.e.

• Analytical Science and Technology
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• v.29 no.2
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• pp.65-72
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• 2016

This study presented an analytical method for detecting radium in soils using a liquid scintillation counter (LSC). The isotope ²²⁶Ra was extracted from soil using the fusion method and then separated from interfering radionuclides using the precipitation method. Radium was coprecipitated as sulfate salts with barium (Ba) and then converted into Ba(Ra)CO₃, which is soluble in an acidic solution. The isotope ²²²Rn, the decay progeny of ²²⁶Ra, was trapped in a water immiscible cocktail and analyzed by LSC. The pulse shape analysis (PSA) level was estimated using ⁹⁰Sr and ²²⁶Ra standard solutions. The figure of merit was the highest at PSA 80, while the alpha spillover was the lowest at PSA 80. The counting efficiency was 243 ± 2% in a glass vial. This analytical method was verified with International Atomic Energy Agency (IAEA) reference materials, including IAEA-312, IAEA-314, and IAEA-315. The recovery ranged from 60–82%, while the relative bias between the measured value and the recommended value was less than 10%. The minimum detectable activity was 2.1 Bq kg⁻¹ with dry mass 1 g, the background count rate of 0.02 cpm, the recovery rate of 70% and counting time of 30 min.