• Journal of the Institute of Electronics and Information Engineers
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• v.53 no.9
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• pp.143-147
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• 2016

Recently, digital tomosynthesis system (DTS) has been developed to reduce overlap using conventional X-ray and to overcome high patient dose problem using computed tomography (CT). The purpose of this study was to develop image reconstruction algorithm and to evaluate image characteristics and dose with chest digital tomosynthesis (CDT) system. Image reconstruction was used for filtered back-projection (FBP) methods and system geometry was constructed ${\pm}10^{\circ}$, ${\pm}15^{\circ}$, ${\pm}20^{\circ}$, and ${\pm}30^{\circ}$ angular range for acquiring phantom images. Image characteristics carried out root mean square error (RMSE) and signal difference-to-noise ratio (SDNR), and dose is evaluated effective dose with ${\pm}20^{\circ}$ angular range. According to the results, the phantom image with slice thickness filter has superb RMSE and SDNR, and effective dose was 0.166 mSv. In conclusion, we demonstrated usefulness of developed CDT image reconstruction algorithm and we constructed CDT basic output data with measuring effective dose.

• Journal of Radiation Protection and Research
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• v.14 no.2
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• pp.10-17
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• 1989

A study for the assessment of dose given by outdoor radon to respiratory system has been carried out by making use of radon-cups containing CR-39 plastic track detectors. Detection efficiencies were determined by irradiation of the radon-cups in a standard radon chamber of known concentration. Thus determined detection factors of CR-39 plastic track detector in bare, open cup and filtered cup geometry are found to be 0.273, 0.0813 and 0.0371 $trmm^{-2}$/(37$Bqm^{-3}{\cdot}d$), respectively, which are chemically etched in 30% NaOH solution of $70^{\circ}C$ for 220 minutes. The outdoor radon concentrations measured at Taejeon(Chungnam National University) from May 1988 to March 1989 are in the range of 27.4 - 135.8 Bq/$m^3$(0.74 - 3.67pCi/l)by open cup and 16.7 - 143.9 Bq/$m^3$(0.45 - 3.89 pCi/l) by filtered cup, which yield overall annual average value of outdoor radon concentration of $70.8Bq/m^3$(1.91 pCi/l). Corresponding effective dose equivalent rate to respiratory system of ICRP standard man is assessed to be 520 nSv /h.

• Journal of Radiation Protection and Research
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• v.24 no.4
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• pp.205-213
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• 1999

Effective dose conversion coefficients from unit activity radionuclides contaminated on the ground surface were calculated by using MCNP4A rode and male/female anthropomorphic phantoms. The simulation calculations were made for 19 energy points in the range of 40 keV to 10 MeV. The effective doses E resulting from unit source intensity for different energy were compared to the effective dose equivalent $H_E$ of previous studies. Our E values are lower by 30% at low energy than the $H_E$ values given in the Federal Guidance Report of USEPA. The effective dose response functions derived by polynomial fitting of the energy-effective dose relationship are as follows: $f({\varepsilon})[fSv\;m^2]=\;0.0634\;+\;0.727{\varepsilon}-0.0520{\varepsilon}^2+0.00247{\varepsilon}^3,\;where\;{\varepsilon}$ is the gamma energy in MeV. Using the response function and the radionuclide decay data given in ICRP 38, the effective dose conversion coefficients for unit activity contamination on the ground surface were calculated with addition of the skin dose contribution of beta particles determined by use of the DOSEFACTOR code. The conversion coefficients for 90 important radionuclides were evaluated and tabulated. Comparison with the existing data showed that a significant underestimates could be resulted when the old conversion coefficients were used, especially for the nuclides emitting low energy photons or high energy beta particles.

• Journal of the Korean Society of Radiology
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• v.9 no.6
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• pp.357-362
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• 2015

This study was to evaluate the usefulness through the comparison of patients group and healthy control group by acquiring a variety of functional parameters index from time-activity curves of salivary gland scan using 99mTc-pertechnetate. From December 2014 to February 2015, had the targets of 30 patients with dry mouth and 10 people in healthy control group underwent the salivary gland scan. After intravenous injection of 370 MBq of 99mTc-pertechnetate, Vitamin C powder stimulation was administerd orally at 20 min and then 10 minutes were taken scan. The method of quantitative analysis was as follows, the time-activity curve was drawn after the parotid gland and submandible gland were prescribed as a region of interest, a variety of function parameters index was obtained in each position of the curve, and the patients group and the control group were compared. As for the methods applied in comparison and measurement, uptake ratio (UR), time at maximum counts (Tmax), time at minimum counts (Tmin), maximum accumulation (MA), accumulation velocity, maximum secretion (MS), maximum stimulation secretion (MSS), and secretion velocity (SV) were used. In the comparison of functional parameters index of patient group and normal group, the healthy normal group showed significant difference compared to the patient group in all indices except for the minimum radioactivity time (Tmin), and also in terms of variation over time the normal group showed significant difference compared to the patient group (p<0.05). Consequently, it was considered that the quantitative analysis that used a variety of function parameters index would be useful for evaluating the function of the salivary glands of the patients with dry mouth as an objective and standardized information.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.13 no.5
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• pp.2278-2284
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• 2012

Exposure-dose reducing effect was measured by using bolus, a tissue-equivalent material as a shield to obtain useful diagnostic images while minimizing the radiation exposure of thyroid which is highly sensitive to radiation during panoramic radiography. The experiment was performed within the period of 1 June 2001 through 30 June 2011 by measuring entrance surface dose and deep dose at the thyroid-corresponding site of a head and neck phantom. As a result, the entrance surface dose in the thyroid for using no shield was 43.84 ${\mu}Gy$ on the average, and the thyroid shield of bolus 10 mm in thickness reduced the dose by 15.45 ${\mu}Gy$(35.24%) to 28.39 ${\mu}Gy$ on the average. The use of a 20 mm thyroid shield resulted in the dose of 25.38 ${\mu}Gy$ on the average, a 18.46 ${\mu}Gy$(42.10%) drop from 43.84 ${\mu}Gy$ for using no shield. On the site 20 mm below the surface, a thyroid shield 10 mm in thickness had no dose-reducing effect, while a 20 mm thyroid shield reduced the dose by 0.06 mSv(20%).

• Korean Journal of Soil Science and Fertilizer
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• v.31 no.4
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• pp.384-391
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• 1998

Nutrient removal during stem harvest was evaluated in a one-year rotation willow bioenergy plantation. For the stem nutrient content, the stem biomass and stem nutrient concentration were collected in the winter of 1987-1993 from the established willow plantation at Tully, New York, U.S.A. in 1987. Five willow clones and one hybrid poplar clone were planted. Half of the plots were fertilized annually with $336kg\;ha^{-1}$ N, $112kg\;ha^{-1}$ P, and $224kg\;ha^{-1}$ K. All trees were harvested annually. Mean annual nutrient removals of N, P, K, Ca, and Mg by annual stem harvesting over seven years were respectively 30-70, 4-10, 14-40, 19-59 and $3-5kg\;ha^{-1}$. Fertilized plants exported higher quantities of nutrients than non-fertilized ones. Nontheless, quantities of nutrients exported were well below the quantities supplied by fertilization suggesting that nutrients removal by stem harvesting is not likely to cause a decrease in soil fertility. However, in non-fertilized plots, the amount of nutrients removed could result in decrease of nutrient availability and soil fertility over the long-term. An evaluation of the clones revealed that clone SV1 is the most nutrient efficient.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.12 no.9
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• pp.4274-4282
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• 2011

In this study, Fenton reaction was studied for the possibility of applying as advanced treatment and its optimal condition for the removal of refractory organics from the dye wastewater. Fenton reaction was applied to remove refractory organics after the bio-treatment (secondary treatment) inside test laboratory and on-site pilot plant. Wastewater from the secondary treatment was used and its $COD_{Mn}$ was measured as 30~50mg/L. After the Fenton reaction, the optimal condition was found as pH 3~3.5, reaction time 2~2.5hr, chemical input ratio of ($FeCl_2$(33%)/$H_2O_2$(35%)) was 3 : 1. When chemical input ratio of ($FeCl_2$(33%)/$H_2O_2$(35%)) was at its optimal, amount of sludge volume ($SV_{2hr}$) was 21~28%. With pilot plant test, removal rate was heavily influenced by the hydraulic retention time(HRT), and optimum value of HRT was 2.0 hr. When pilot plant($2m^3/d$) was placed on-site and operated continuously, it showed steady and fairly good treatment of COD where COD removal rate was 60~70%, treated water showed below 20mg/L.

• Journal of the Korean Society of Radiology
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• v.14 no.7
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• pp.857-862
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• 2020

In March 2011, a tsunami off Japan caused radioactive material that had seeped into the sea from the Fukushima nuclear accident to flow to the Pacific Ocean, causing pollution to sea life. For a comparative evaluation with the area surrounding the site of a nuclear power plant by the release of radioactive materials, an area 20 to 30 km away from the emergency protection plan area was selected as a comparative point considering weather conditions, population distribution, etc. In addition, the government intends to analyze the minimum detection radiation received by residents around the nuclear power plant and evaluate the effective dose. Analysis of tritium radiation from water samples showed that most of the samples were not detected and that 0.0014 % to 0.777 % of the annual legal standard of 1 mSv for the general public had little effect on the human body. Therefore, the measurement and analysis of water samples around the nuclear power plant site is expected to help relieve anxiety, such as exposure to the general public and neighboring residents due to radiation release.

• The Korean Journal of Nuclear Medicine Technology
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• v.14 no.2
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• pp.65-76
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• 2010

Purpose: he use of PET scanners and the number of patient in Korea have been increased for recent several years dramatically. For this reason, technologists have more possibilities to be exposed to the radiation. The hospitals using PET scanners should make an effort to reduce the radiation exposure dose. The purpose of this study was to evaluate the radiation exposure does when using radiation shielding devices. The evaluation was performed through questionnaire survey and experiment. Materials and Methods: First, the technologists who had experience working in PET center in 2008-2009 were surveyed with questionnaire and TLD Figures, personal opinion of utilization of radiation shielding devices are analyzed. Second, we measured the shielding rate of shielding devices which have been using in PET study procedures. We divided the procedures into four steps; distribution, moving, injection of $^{18}F$-FDG and patient setup. Results: First, the results of this survey, using of L-block+Syringe shield, L-block, Syringe shield, No shield during the injection, were each 58.5%, 20%, 9%, 12.3%. The TLD values according to utilization of radiation shield, using both L-block+Syringe Shield and L-block showed the lower TLD values, and Syringe shield only or No shield showed the higher TLD values. Second, the results of experiments according to PET study procedures measured the shielding rates as follows. The shielding rates during the distribution using L-block, L-block+Apron shield were measured 97.4%, 97.7%. The shielding rates during the $^{18}F$-FDG delivery to the injection room using mobile Syringe shield, Syringe holder, Syringe shield carrier were each 81.7%, 98.9%, 99.7%. The shielding rates during the injection using Syringe shield, L-block, L-block+Syringe shield were measured each 51.9%, 98.3%, 98.7%. The shielding rates of Apron were measured in each 30, 60, 90, 120, 150 cm distance. The measurement were each 16.9%, 14.2%, 16.6%, 17.1%, 18.1%, 18.6%. Conclusion: The most effective method for radiation shielding is to using L-block during the $^{18}F$-FDG distribution and Syringe shield carrier during in moving $^{18}F$-FDG. For the $^{18}F$-FDG injection, L-block+Syringe shield have to be used. The shielding effect of Apron has shown average 16.4%. According to the survey of questionnaire, the operators recognized well risk of the radiation exposure but, tended ignore in working. The radiation dose according to recognition of radiation exposure risk was not relevant. but radiation dose according to utilization of radiation shield lower the more use it. The main reason of no use of shielding devices is cumbersome, 55% of the respondents answered. I'm sure, by use of radiation shield in all PET procedure, radiation exposure will be reduced considerably.

• Journal of Radiation Protection and Research
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• v.22 no.4
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• pp.227-235
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• 1997

Cytogenetic studies were performed in peripheral blood lymphocytes from hospital workers occupationally exposed to low doses of radiation (0.30 - 40.07mSv). The workers were divided into three groups according to their job area : 18 diagnostic radiology, 17 therapeutic radiology, and 16 nuclear medicine. The control group consisted of 49 non-radiation workers with no history of exposure to radiation. A higher percentage of cells with aberration(1.275%) was observed in the workers compared to the controls(0.677%) and the difference was statistically significant(p<0.001). The frequency of chromosomal aberration was $0.706{\times}10^{-2}$/cell in the exposed and $0.344{\times}10^{-2}$/cell in the control(p<0.05). Chromosomal exchange frequency was $0.083{\times}10^{-2}$/cell in the control vs $0.245{\times}10^{-2}$/cell in the workers. There was no evidence of significant increase of chromosome aberration related to age or to the duration of employment. The frequency of chromosomal exchange in workers of nuclear medicine was $0.313{\times}10^{-2}$/cell, which was significantly higher than in the control($0.083{\times}10^{-2}$/cell) or other working groups: therapeutic radiology($0.265{\times}10^{-2}$/cell), and diagnostic radiology($0.167{\times}10^{-2}$/cell). No dose-effect relation was found between chromosome aberration and total cumulative doses, recent 5 yr, recent 2 yr cumulative dose. But in case of last 1 yr cumulative dose, dose-dependant increase was observed when controls were considered(p<0.05). The radiation dose which workers have received was much lower than the maximum permissible dose, but there was a significant difference in the frequency of chromosome aberration between occupationally exposed workers and control. So, it is clear that chromosome aberration is a quite sensitive indicator of radiation exposure and it can be detected at very low dose level of occupational exposure.