• Journal of Radiation Protection and Research
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• v.13 no.2
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• pp.9-20
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• 1988

In order to quantify the contribution of cosmic-ray ionizing component to the dose given by natural background radiation, a series of measurement has been carried out using LiF TLDs for about one and a half years on quarterly basis. Three different types of LiF TLDs namely, chips and PTFE based disks of $^{7}LiF$, and the same disks of $^{6}LiF$ for identifying possible contribution of neutron component were used. Measurements were made by placing badge-incased TLDs in a lead castle of 10 to 15cm thick installed in a room on the third floor of a four-story building in CNU Daedeok campus for 5 cycles of 90 days. For comparison a series of spectrometric study was also performed for the energy region over 3MeV using a 3'${\phi}\;{\times}\;3$'NaI(Tl) scintillation detector in association with an MCA of 1024 channels, and it was found that the data obtained by the TLDs placed in the lead castle indicate 75% of the dose given by outdoor cosmic-ray component. The results obtained by the TLDs through correction for shielding loss show that the outdoor dose contribution of ionizing component of cosmic rays at this campus is $34.3{\pm}1.1nGy/h$ which satisfactorily agrees with that expected for our particular location of measurement.

• Journal of radiological science and technology
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• v.33 no.4
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• pp.327-334
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• 2010

Exposure during childhood results in higher risk for certain detrimental cancers than exposure during adulthood. We measured entrance skin dose (ESD) under 7-year children undergoing chest imaging and compared the relationship between ESD and age, height, weight, chest thickness. Though it is important to measure chest thickness for setting up the exposure condition of chest examination, it is difficult to measure chest thickness of children. We set up exposure parameters according to age because chest thickness of children has correlation with age. In the exposure parameters, for chest A-P examination under 2 year-children, tube voltage (kVp) in hospital A was higher than that in hospital B while tube current (mAs) was higher in hospital B, thus the ESD values were about 1.7 times higher in hospital B. However, for chest P-A examination over 4 year-children, the tube voltage was 7 kVp higher in hospital B, the tube current were same in all two systems, and focus to image receptor distance (FID) in hospital B (180 cm) was longer than that in hospital A (130 cm), thus the ESD values were 1.4 times higher in hospital A. For same ages, the ESD values for chest A-P examinations were higher than those for chest P-A examinations. Comparing ESD according to age, ESD values were $154{\mu}Gy$, $194{\mu}Gy$ and $138{\mu}Gy$ for children under 1 year, 1 to under 4 years and 4 to under 7 years of age, respectively. These values were lower than reference level ($200{\mu}Gy$) recommended in JART (japan association of radiological technologists), however these were higher than reference values recommended by EC (european commission), NRPB (national radiological protection board) and NIFDS (national institute of food & drug safety evaluation). In conclusion, the values of ESD were affected by exposure parameters from radiographer's past experience more than x-ray system. ESD values for older children were not always higher than those for younger children. Therefore we need to establish our own DRLs (diagnostic reference levels) according to age of the children in order to optimize pediatric patient protection.

• Journal of radiological science and technology
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• v.37 no.1
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• pp.1-6
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• 2014

Breast shooting performance management and quality control of the generator is applied to the amount of current IEC(International Electrotechnical Commission) 60601-2-45 tube voltage and tube current are based on standards that were proposed in the analysis of the test results were as follows. Tube voltage according to the value of the standard deviation by year of manufacture from 2001 to 2010 as a 42-3.15 showed the most significant, according to the year of manufacture by tube amperage value of the standard deviation to 6.38 in the pre-2000 showed the most significant, manufactured after 2011 the standard deviation of the devices, the PAE(Percent Average Error) was relatively low. This latest generation device was manufactured in the breast of the tube voltage and tube diagnosed shooting the correct amount of current to maintain the performance that can be seen. The results of this study as the basis for radiography diagnosed breast caused by using the device's performance and maintain quality control, so the current Food and Drug Administration "about the safety of diagnostic radiation generator rule" specified in the test cycle during three years of self-inspection radiation on a radiation generating device ensure safety and performance of the device using a coherent X-ray(constancy) by two ultimately able to keep the radiation dose to the public to reduce the expected effect is expected.

• Journal of Radiation Protection and Research
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• v.24 no.2
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• pp.109-120
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• 1999

Residual radiation and radioactivity level in TRIGA Mark-II, III research reactors and facilities at the KAERI Seoul site, which are to be decommissioned, have been measured, analyzed and evaluated to know the current status of radiation and radioactivity level and to establish and to provide the technical requirements for the safe decommissioning of the facilities which shall be applied in minimizing the radiation exposure for workers and in preventing the release of the radioactive materials to the environment. Radiation dose rate and surface radioactivity contamination level on the experimental equipments, floors, walls of the facilities, and the surface of the activated materials within the reactor pool structure were measured and evaluated. Radioactivity and radionuclides in the pool and cooling water were also analyzed. In case of the activated reactor pool structures which are very difficult to measure the radiation and radioactivity level, a computer code Fispin was additionally used for estimation of the residual radioactivity and radionuclides. The radiation and radioactivity data obtained in this study were effectively used as basic data for decontamination and dismantling plan for safe decommissioning of TRIGA Mark-II, III facilities.

• Journal of Radiation Protection and Research
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• v.39 no.1
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• pp.7-13
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• 2014

Phosphate rock, phosphogypsum, and products in phosphate processing facility contain naturally occurring radioactive materials (NORM). Therefore, they may give rise to enhanced radiation dose to workers due to inhalation of airborne particulates. Internal dose due to particle inhalation varies depending on particle properties. The objective of the present study was to characterize particle properties at the largest phosphate processing facility in Korea. A cascade impactor was employed to sample airborne particulates at various processing areas in the plant. The collected samples were used for characterization of particle size distribution, particle concentration in the air, and shape analysis. Aerodynamic diameters of airborne particulates ranged 0.03-100 ${\mu}m$ with the highest concentration at the particle size range of 4.7-5.8 ${\mu}m$ (geometric mean = 5.22 ${\mu}m$) or 5.8-9.0 ${\mu}m$ (geometric mean = 7.22 ${\mu}m$). Particle concentrations in the air varied widely by sampling area up to more than two orders of magnitude. The large variation resulted from the variability of mechanical operations and building ventilations. The airborne particulates appeared as spheroids or rough spherical fragments across all sampling areas and sampled size intervals. Average mass densities of phosphate rocks, phosphogypsums, and fertilizers were 3.1-3.4, 2.1-2.6, and 1.7 $gcm^{-3}$, respectively. Radioactivity concentration of uranium series in phosphate rocks varied with country of origin, ranging 94-866 $Bqkg^{-1}$. Among the uranium series, uranium was mostly concentrated on products, including phosphoric acid or fertilizers whereas radium was concentrated on byproducts or phosphogypsum. No significant radioactivity of $^{226}Ra$ and $^{228}Ra$ were found in fertilizer. However, $^{40}K$ concentration in fertilizer was up to 5,000 Bq $g^{-1}$. The database established in this study can be used for the accurate risk assessment of workers due to inhalation of airborne particles containing NORM. In addition, the findings can be used as a basic data for development of safety standard and guide and for practical radiation safety management at the facility.

• Journal of Radiation Industry
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• v.9 no.4
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• pp.209-216
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• 2015

It has been about 5 years since the Fukushima nuclear power plant accident, which contaminated large area with radioactive materials. It is necessary to assess radiation dose to establish evacuation areas and to set decontamination goal for the large contaminated area. In this study, we assessed temporal trend of radiation dose to the public living in the large area contaminated with radioactive materials after the Fukushima nuclear power plant accident. The dose assessment was performed based on Chernobyl model and RESRAD model for two evacuation lift areas, Kawauchi and Naraha. It was reported that deposition densities in the areas were $4.3{\sim}96kBq\;m^{-2}$ for $^{134}Cs$, $1.4{\sim}300kBq\;m^{-2}$ for $^{137}Cs$, respectively. Radiation dose to the residents depended on radioactive cesium concentrations in the soil, ranging $0.11{\sim}2.4mSv\;y^{-1}$ at Kawauchi area and $0.69{\sim}1.1mSv\;y^{-1}$ at Naraha area in July 2014. The difference was less than 5% in radiation doses estimated by two different models. Radiation dose decreased with calendar time and the decreasing slope varied depending on dose assessment models. Based on the Chernobyl dosimetry model, radiation doses decreased with calendar time to about 65% level of the radiation dose in 2014 after 1 year, 11% level after 10 years, and 5.6% level after 30 years. RESRAD dosimetry model more slowly decreased radiation dose with time to about 85% level after 1 year, 40% level after 10 years, and 15% level after 30 years. The decrease of radiation dose can be mainly attributed into radioactive decays and environmental transport of the radioactive cesium. Only environmental transports of radioactive cesium without consideration of radioactive decays decreased radiation dose additionally 43% after 1 year, 72% after 3 years, 80% after 10 years, and 83% after 30 years. Radiation doses estimated with cesium concentration in the soil based on Chernobyl dosimetry model were compared with directly measured radiation doses. The estimated doses well agreed with the measurement data. This study results can be applied to radiation dose assessments at the contaminated area for radiation safety assurance or emergency preparedness.

• The Journal of Korean Society for Radiation Therapy
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• v.27 no.1
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• pp.1-11
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• 2015

Purpose : Evaluating absorbed dose related to 2D and 3D imaging confirmation devices Materials and Methods : According to the radiographic projection conditions, absorbed doses are measured that 3 glass dosimeters attached to the centers of 0', 90', 180' and 270' in the head, thorax and abdomen each with Rando phantom are used in field size $26.6{\times}20$, $15{\times}15$. In the same way, absorbed doses are measured for width 16cm and 10cm of CBCT each. OBI(version 1.5) system and calibrated glass dosimeters are used for the measurement. Results : AP projection for 2D imaging check, In $0^{\circ}$ degree absorbed doses measured in the head were $1.44{\pm}0.26mGy$ with the field size $26.6{\times}20$, $1.17{\pm}0.02mGy$ with the field size $15{\times}15$. With the same method, absorbed doses in the thorax were $3.08{\pm}0.86mGy$ to $0.57{\pm}0.02mGy$ by reducing field size. In the abdomen, absorbed dose were reduced $8.19{\pm}0.54mGy$ to $4.19{\pm}0.09mGy$. Finally according to the field size, absorbed doses has decreased by average 5~12%. With Lateral projection, absorbed doses showed average 5~8% decrease. CBCT for 3D imaging check, CBDI in the head were $4.39{\pm}0.11mGy$ to $3.99{\pm}0.13mGy$ by reducing the width 16cm to 10cm. In the same way in thorax the absorbed dose were reduced $34.88{\pm}0.93(10.48{\pm}0.09)mGy$ to $31.01{\pm}0.3(9.30{\pm}0.09)mGy$ and $35.99{\pm}1.86mGy$ to $32.27{\pm}1.35mGy$ in the abdomen. With variation of width 16cm and 10cm, they showed 8~11% decrease. Conclusion : By means of reducing 2D field size, absorbed dose were decreased average 5~12% in 3D width size 8~11%. So that it is necessary for radiation therapists to recognize systematical management for absorbed dose for Imaging confirmation. and also for frequent CBCT, it is considered whether or not prescribed dose for RT refer to imaging dose.

• Journal of Radiation Protection and Research
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• v.37 no.3
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• pp.108-115
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• 2012

The Urban Areas Working Group within the EMRAS-2 ($\underline{E}$nvironmental $\underline{M}$odelling for $\underline{RA}$diation $\underline{S}$afety, Phase 2), which has been supported by the IAEA (International Atomic Energy Agency), has designed some types of accidental scenarios to test and improve the capabilities of models used for evaluation of radioactive contamination in urban areas. For the comparison of the results predicted from the different models, the absorbed doses in air were analyzed as a function of time following the accident with consideration of countermeasures to be taken. Two kinds of considerations were performed to find the dependency of the predicted results. One is the 'accidental season', i.e. summer and winter, in which an event of radioactive contamination takes place in a specified urban area. Likewise, the 'rainfall intensity' on the day of an event was also considered with the option of 1) no rain, 2) light rain, and 3) heavy rain. The results predicted using a domestic model of METRO-K have been submitted to the Urban Areas Working Group for the intercomparison with those of other models. In this study, as a part of these results using METRO-K, the countermeasures effectiveness in terms of dose reduction was analyzed and presented for the ground floor of a 24-story business building in a specified urban area. As a result, it was found that the countermeasures effectiveness is distinctly dependent on the rainfall intensity on the day of an event, and season when an event takes place. It is related to the different deposition amount of the radionuclides to the surfaces and different behavior on the surfaces following a deposition, and different effectiveness from countermeasures. In conclusion, a selection of appropriate countermeasures with consideration of various environmental conditions may be important to minimize and optimize the socio-economic costs as well as radiation-induced health detriments.

• Journal of the Korean Society of Radiology
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• v.5 no.5
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• pp.303-308
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• 2011

Background/Aims : The increasing use of diagnostic and therapeutic interventional radiology calls for greater consideration of radiation exposure risk to radiologist and radiological technician, and emphasizes the proper system of radiation protection. This study was designed to assess the effect of a protective grass shield. Methods : A protective grass was following data depth, 0.8 cm; width, 100 cm; length, 100 cm, lead equivalent, 1.6 mmPb. The protective shield was located between the patient and the radiologist. Thirty patients (13 male and 17 female) undergoing interventional radiology between September 2010 and December 2010 were selected for this study. The dose of radiation exposure was recorded with or without the protective grass shield at the level of the head, chest, and pelvis. The measurement was made at 50 cm and 150 cm from the radiation source. Results : The mean patient age was 69 years. The mean patient height and weight was $159.7{\pm}6.7$ cm and $60.3{\pm}5.9$ kg, respectively. The mean body mass index (BMI) was $20.5{\pm}3.0$ kg/m2. radiologists received $1530.2{\pm}550.0$ mR/hr without the protective lead shield. At the same distance, radiation exposure was significantly reduced to $50.3{\pm}85.2$ mR/hr with the protective lead shield (p-value<0.0001). The radiation exposure to radiologist and radiological technician was significantly reduced by the use of a protective lead shield (p value <0.0001). The amount of radiation exposure during interventional radiology was related to the patient' BMI (r=0.749, p=0.001). Conclusions : This protective shield grass is effective in protecting radiologist and radiological technician from radiation exposure.

• The Korean Journal of Nuclear Medicine Technology
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• v.18 no.1
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• pp.82-88
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• 2014

Purpose: The purpose of study was to evaluate radiation dose for pediatric patients by changing tube voltage (kVp) and tube current (mA) at minimum conditions. By evaluating radiation dose, we want to provide dose reduction for pediatric patients and maintain good quality of SPECT/CT images. Materials and Methods: Discovery NM/CT 670 Scanne was used as SPECT/CT. Tube voltages are 80 and 100 kvP. Tube currents are 10, 15, 20, 25 mA. Using PMMA (Polymethyl methacrylate) Phantom, radiation dose which were calculated at center and peripheral dose and SNRD (Signal to Noise Ratio Dose) were evaluated. Using the CT performance phantom, spatial resolution was evaluated as the MTF (Modulation Transfer Function) graph. Jaszczak phantom was used for SPECT image evaluation by CNR (Contrast to Noise to Ratio). Results: Radiation dose using the PMMA phantom was higher peripheral dose than center dose about 7%. SNRD were 7.8, 8.2, 8.3, 8.8, 8.8, 9.9, 9.8, 9.6 for 80 kVp 10, 15, 20, 25 mA, 100 kVp 10, 15, 20, 25 mA. We can distinguish 35, 45, 70, 71, 52, 58, 90, 110 linepair for 80 kVp 10, 15, 20, 25 mA, 100 kVp 10, 15, 20, 25 mA at resolution with MTF. CNR of SPECT images using CT attenuation map were 57.8, 57.7, 57.1, 56.7, 56.6, 56.7, 56.7, 56.7% for 80 kVp 10, 15, 20, 25 mA, 100 kVp 10, 15, 20, 25 mA. Conclusion: In this study, radiation dose for pediatric patients showed decreased low dose condition. And SNRD value was similar in all condition. Resolution showed higher value at 100kVp than 80kVp. for CNR, there was no significant difference. we should take additional study to prove better quality and dose reduction.