• Progress in Medical Physics
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• v.11 no.2
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• pp.123-130
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• 2000

The performance of an electrometer directly affects on the accuracy and precision in radiation dosimetry. This study is to list of the quality control for maintaining performance and to perform evaluation tests of an electrometer. Performance tests selected include proper polarizing voltages, warm-up and equalization time, leakages, long-term stability, linearity, and effect of ambient conditions. An electrometer connected with a rigid stem ionization chamber was evaluated with a Strontium-90 check device. Bias voltage was measured directly on the input socket. Equalization time is the time required for reaching threshold of charged state after the power is on or the bias voltage is changed. Pre- and post-signal leakages are defined as the accumulation of signal with no exposure and after exposure, respectively. Over three months period, the electrometer's long-term stability was measured by comparison of the temperature-pressure corrected readings. Linearity was expressed as the deviation of readings from multiple short exposures from one continuous exposure. Effect of ambient conditions was expressed as the zero drift of the electrometer over 17-34$^{\circ}C$ temperature ranges. For two nominal values, 300 and 500 volts, measured voltages were lower by 2.5 and 5.8%, respectively. The warm-up time, 20 minutes, was longer than the lamp time by 9 minutes and the equalization time was less than 1 minute. Without exposure, the zero-drift was 0.002 scale-unit in 15 minutes and the leakage after 10 minutes exposure was minimal. The IQ-4 was stable over 99.4% for three-month periods. Deviation from the linearity was 0.9% for measurement scale, 0.000-9.991. Over 17-34$^{\circ}C$ temperature range, the zero-drift was minimal, less than 0.2%. For a clinically-used electrometer, a list for the basic peformance evaluations is proposed. By running this program, the measurement error using an electrometer can be reduced and in turn the improvement in accuracy and precision of radiation dosimetry can be achieved.

• Journal of Radiation Protection and Research
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• v.19 no.2
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• pp.121-132
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• 1994

This study concerns about the measurement and the investigation of environmental radiation characteristics which the components and the distribution of exposure rates by terrestrial y-rays in Taegu area. $4^{'}{\phi}{\times}4^{'}$ NaI(T1) scintillation detector with a multichannel analyzer was used in the measurement of y-rays as a part of in-situ spectrometry at twenty eight different locations in this area. The conversion into the exposure rate from the measured ${\gamma}-ray$ spectrum has been carried out leading to a net exposure rate and component ones by $^{40}K,\;^{238}U$ series and $^{232}Th$ series products which are known by the major parts in the terrestrial ${\gamma}-rays$ generally. As a result, the average exposure rate by the terrestrial ${\gamma}-rays$ in Taegu area is $9.4{\mu}R/h$ and the distribution of individual exposure rates shows more or less differences between these locations even after the consideration of diurnal and yearly variations which are always involved in these measurements. The component parts of exposure rates are distributed $^{40}K\;2.9{\sim}4.6{\mu}R/h,\;^{238}U$ series $1.2{\sim}3,\;1{\mu}R/h,\;^{232}Th$ series $2.5{\sim}5.0{\mu}R/h$ over the measured locations.

• Korean Journal of Veterinary Research
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• v.44 no.3
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• pp.343-348
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• 2004

Cytogenetic and hematological analysis was performed in peripheral blood of cattle in the vicinity of Uljin nuclear power station and control area. The frequency of micronuclei(MN) in peripheral blood lymphocytes from cattle was used as a biomarker of radiobiological effects resulting from exposure to environmental radiation. An estimated dose of radiation was calculated by a best fitting linear-quadratic model based on the radiation-induced MN formation from the bovine lymphocytes exposed in vitro to radiation over the range from 0 Gy to 4 Gy. MN ratio in lymphocytes of cattle from Uljin nuclear power station and control area were 8.90/1,000 and 9.60/1,000, respectively. There were no significant differences in MN frequencies and hematological values in cattle between Uljin and control area.

• Journal of Radiation Protection and Research
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• v.30 no.4
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• pp.175-183
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• 2005

Dose distribution of Korean radiation workers classified by occupational categories was analyzed. Statistics of the occupational radiation exposure(ORE) in 2002 of the radiation workers in diagnostic and dental radiology were obtained from the Korea Food and Drug Agency(KFDA) who maintains the database for individual radiation dose records. Corresponding statistics for the rest of radiation workers were obtained by processing the individual annual doses provided by the Korea Radioisotope Association(KRIA) after deletion of individual information. The ORE distribution was classified in term of 28 occupational categories, annual individual dose levels, age groups and gender of 52733 radiation workers as of the year of 2002. The total collective dose was 66.4 man-Sv and resulting average individual ORE was 1.26 mSv. Around 80% of the workers were exposed to minimal doses less than 1.2 mSv. However, it appeared that the recorded doses exceeded 20 mSv for 43 workers in the industrial radiography and for 147 workers in the field of radiology. Particularly, recorded doses of 23 workers in radiology exceeded the annual dose limits of 50 mSv, which is extraordinary when the working environment is considered. It is uncertain whether those doses are real or caused by careless placing of dosimeters in the imaging rooms while the X-ray units are in operation. No one in the workforce of 16 operating nuclear power plant units was exposed over 20 mSv in 2002. Number of workers was the largest in their 30's of age and the mean individual dose was the highest in their 20's. Women were around 20% of the radiation workers and their average dose was around one half of that of man workers.

• Journal of Radiation Protection and Research
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• v.32 no.3
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• pp.97-104
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• 2007

The corelation between the indoor volume and the measured radon concentration has been analyzed by comparing the radon concentration and the indoor volume of apartment rooms in Jeonju City. We also measured the annual exposure dose based on the variation in indoor radon concentration over time. To do this, we took 8 larger rooms and 8 smaller rooms of apartment, respectively, as a sample. The average volume of the larger rooms and that of the smaller rooms were $31.59\;m^3$ and $16.82\;m^3$, respectively. The average radon concentration of the larger rooms and that of the smaller rooms turned out to be $71.73\;Bq/m^3$ and $108.51\;Eq/m^3$, respectively. indicating that indoor volume is in inverse proportion to the radon concentration, i.e., the bigger the ratio of the surface area/volume, the higher the indoor radon concentration. From the measurement of the variation in indoor radon concentration over time fur a single day, the average intraday radon concentration variation was found to be about $46.8\;Bq/m^3$. The highest level of concentration ($114.5\;Bq/m^3$) was measured between 8 and 10 AM and the lowest level of concentration ($67.7\;Bq/m^3$) between 2 and 4 PM. The annual exposure dose turned out to be in the range of 0.3 mSv/yr to 2.16 mSv/yr, showing that the dose in some apartments exceeded 1.3 mSv/yr, the numerical value presented by the United Nations Scientific Committee on the Effects of Atomic Radiation (UNSCEAR).

• Korean Journal of Digital Imaging in Medicine
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• v.12 no.2
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• pp.71-79
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• 2010

Thanks to the great development of technology in radiation, we are now able to reduce radiation exposure to the patients, and the radiographer and expenses in medical sector. We are also trying to produce ideal images which maintain useful information. These kinds of effort are increasing over the world. For that reason, we should get images which include necessary data of patients. Then it also can help to reduce radiation exposure to the patients. Therefore, we need to know the problems that cause a falling off in image's quality and check on generator in case of their electronic and mechanical errors. And moreover, we should anticipate the possibility of devices errors and prevent them with regular quality control. This investigation was conducted in medical institutions, institute of educations and hospitals. They are all in Seongnam-City. We used PMX-III, kVp meter to implement kVp test, mR / mAs output test, light fiel / beam alignment test, Reproducibility of exposure dose, half value layer test, reproducibility of exposure time test. in the case of hospitals, they perceive the importance of regular quality control and organize the regular quality control team so they can be satisfied with the error standard in most experiments. On the other hand, when it comes to medical institutions and institute of educations, they perceive the importance of regular quality control less than hospitals do. Radiographer need to understand the importance of regular quality control and practice it so they can get the fine ideal image with the lower dose to the patient.

• Journal of the Korean Society of Radiology
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• v.6 no.6
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• pp.465-471
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• 2012

In this study, three dimensional X-ray dose distribution from dental X-ray generator system was measured by ALOKA PDM-117 dosimeter. The X-ray dose distribution will be change with XCP-DS FIT in oral shot, because the distance between X-ray generator and the dosimeter. The X-ray dose change affects on patient exposure and radiograph image quality. Therefore, it is important to obtain relation between the X-ray dose and the distance. The X-ray dose at the central position was decreased with increasing the distance. Furthermore, the dose at the edge of the X-ray flux was increased with increasing the distance. The increased dose affects on the patient radiation exposure. The present results will provide for good dental radiograph image and reducing radiation over-exposure on patient.

• Journal of radiological science and technology
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• v.44 no.5
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• pp.495-502
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• 2021

This study aims to provide basic data for elderly health insurance policy and medical radiation safety management by analyzing the general radiography usage and exposure dose of the elderly in Korea. The effective dose for each general radiography was calculated using the ALARA-GR program for 260 general radiography codes selected from 'National Health Insurance Care Benefit Cost'. The usage of general radiography was analyzed in the 2016 elderly patient data of the Health Insurance Review and Assessment Service, and the effective dose for each general radiography was applied. The general radiography usage and exposure dose per person aged 65 years and over was 6.47 cases and 0.56 mSv. Females showed higher value than males as 7.15 cases and 0.66 mSv(p<.001). By age, those between 75 and 79 showed the highest number as 6.97 cases and 0.62 mSv(p<.001). Those who were supported by Medical Aid showed higher value than those who were insured by National Health Insurance as 8.82 cases and 0.76 mSv(p<.001). In addition, the ratio by radiography was in the order of Chest 20.85%, Knee Joint 15.58%, and L-spine 14.67%, and the exposure dose was L-spine 29.40%, Chest 15.82%, Abdomen 7.97%, and Entire Spine 7.20%. General radiography, which is widely used due to the high frequency of diseases in the elderly population should be taken into consideration when establishing health insurance policies. In addition, it is necessary to check whether the general radiography with high exposure dose is performed as a routine examination without considering medical necessity.

• Journal of Radiation Protection and Research
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• v.40 no.3
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• pp.162-167
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• 2015

Although the perfomance indicators of the nuclear power plants in Korea show optimal, it requires detailed analysis and discussion centered on the radiation dose. As analysis methods, analysis on the radiation dose of nuclear power plants over the past five years was assessed by comparing the relevant radiation dose of radiation workers and per capita average annual radiation dose of the world's major nuclear power stations was also analyzed. The radiation workers over the annual radiation dose limit of 50 mSv were not. The contrast ratio of the radiation exposure according to the reactor type was the normal operation of PHWR was 6.2% higher than those of the PWR. This shows the radiation work of PHWR during normal driving operation is much more than those of PWR. According to the Performance Indicators of the World Association of Nuclear Operator, the annual radiation dose per unit in 2013 showed 527 man-mSv of Korea is the best country among the major nuclear power generating states, the world average was 725 man-mSv. The annual per capita radiation dose is about 80% less than 1 mSv of the public dose limit and also the average per capita dose showed a very low level as 0.82 mSv. Workers in related organizations showed 1.07 mSv, the non-destructive inspection agency workers showed 3.87 mSv. The remarkable results were due to radiation reduced program such as development of radiation shielding and radiation protection. In conclusion, the radiation exposured dose of nuclear power plants workers in Korea showed a trend which is ideally reduced. But more are expected to be difficul and the psychological insecurity against the operation of the nuclear power plants is existed to the residents near the nuclear power plants. So the radiation dose reduction policy and radiation dose follow up study of nuclear power plants will be continously excuted.

• Korean Journal of Digital Imaging in Medicine
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• v.11 no.1
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• pp.21-26
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• 2009

In operation room, the use of the C-arm unit is increasing. So, the radiation dose of the person who work in operation room was even more increased than before. Thus, this study is shown the measurement of expose dose and the way for decrease of the radiation dose by using the C-arm unit. The experiment was performed with the C-arm unit and used a phantom which is similar to tissue of the human body and fluoro-glass dosimeter for dose measurement. The expose dose were measured by the tube position(over tube, under tube) of the C-arm unit, distance(50, 100$\sim$200cm), direction(I, II, III, IV), runtime(1min, 3min), wearing of the apron. The radiation dose was decreased twice and three times at under tube rather than over tube. The I direction was measured 20$\sim$30% more than the others. The biggest expose dose is 50cm from center on distance. The expose dose is decreased to far from center. In case of Wearing of the apron, the radiation dose was decreased 60$\sim$90% by the distance. But there weren't change of the radiation dose by C-arm tube position. In present, by increasing the usage of the C-arm unit, the radiation dose is inevitable. So, this study recommends us to use the under tube of the C-arm unit. Also, Wearing of the apron is required for minimum of the radiation exposure.