• Asian Pacific Journal of Cancer Prevention
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• v.14 no.10
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• pp.5705-5711
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• 2013

Background: Embryonic stem cells (ESCs) have the potential to form teratomas when implanted into immunodeficient mice, but data in immunocompetent mice are limited. We therefore investigated teratoma formation after implantation of three different mouse ESC (mESC) lines into immunocompetent mice. Materials and Methods: BALB/c mice were injected with three highly germline competent mESCs (129Sv, BALB/c and C57BL/6) subcutaneously or under the kidney capsule. After 4 weeks, mice were euthanized and examined histologically for teratoma development. The incidence, size and composition of teratomas were compared using Pearson Chi-square, t-test for dependent variables, one-way analysis of variance and the nonparametric Kruskal-Wallis analysis of variance and median test. Results: Teratomas developed from all three cell lines. The incidence of formation was significantly higher under the kidney capsule compared to subcutaneous site and occurred in both allogeneic and syngeneic mice. Overall, the size of teratoma was largest with the 129Sv cell line and under the kidney capsule. Diverse embryonic stem cell-derived tissues, belonging to the three embryonic germ layers, were encountered, reflecting the pluripotency of embryonic stem cells. Most commonly represented tissues were nervous tissue, keratinizing stratified squamous epithelium (ectoderm), smooth muscle, striated muscle, cartilage, bone (mesoderm), and glandular tissue in the form of gut- and respiratory-like epithelia (endoderm). Conclusions: ESCs can form teratomas in immunocompetent mice and, therefore, removal of undifferentiated ESC is a pre-requisite for a safe use of ESC in cell-based therapies. In addition the genetic relationship of the origin of the cell lines to the ability to transplant plays a major role.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.30 no.5
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• pp.759-770
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• 1997

The general flow patterns in the Cheju Strait have been investicated by analyzing the current observations measured in $1986\~1989$ by current meter mooring in 3 north-south sections in the Cheju Strait and at 4 observation points around Cheju Harbour, and measured in $1981\~1987$ by drogue tracking. 1. In the Cheju Strait, there are eastward or northeastward residual currents, which implies that sea waters flow into through the whole western section and flow out through the whole eastern section in the Cheju Strait. The velocity of residual currents are $5.2\~30\;cm/sec$ in 10 m layer and $1.3\~24cm/sec$ in mid-bottom layer. Generally, the flow is strong along the deepest through and the northern part, and weak in the shallow areas near Chuja Islands and Bogil Island. 2. In the western entrance of the Cheju Strait, the observed mean residual velocity is 6.93 cm/sec and the volume transport is 0.384 Sv. There are a big discrepancy between the observed residual currents and the geostrophic currents. 3. Near the frontal areas northwest to Chuja Islands, warm and saline offshore waters, flow northward about 5 miles into the southern coastal areas of the Korean Peninsula in flood, and flow back rather eastward or southeastward than southward in ebb. So, warm and saline waters flow along coastal areas, being mixed with coastal waters. As a result, the northwestern area of Chuja Islands plays a role of the entrance of influx of warm and saline offshore water to the southwestern coastal areas of the Korean Peninsula. It should be stressed that this flow pattern is not due to the residual flows, but to the temporal (tidal) flows.

• Journal of the Korean Society of Radiology
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• v.14 no.2
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• pp.169-178
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• 2020

The number of CT scans is increasing every year due to the improvement of the medical standards of the public, and thus the annual dose of medical radiation is also increasing. In this study, we evaluated the effective dose of the human body exposed to CT scans and estimated LAR. First, five region were selected from the CT diagnostic reference level guideline, and the effective dose of human body exposed to each examination was evaluated by clinical CT device. Second, the human organs and effective dose were calculated using the ALARA-CT program under the same conditions. Third, lifetime attributable risk (LAR) estimated by the effective dose exposed through the previous CT scan was estimated. As a result, the most effective dose was 21.18 mSv during the abdomen 4 phase scan, and the dose level was below DRL for all other tests except for the abdominal examination. As a result of evaluating effective dose using a dose calculation program under the same conditions, the results showed about 1.1 to 1.9 times higher results for each examination. In the case of organ dose, the closer the organ to the scan site, the higher the scattering ray. The lifetime attributable risk to CT radiation dose in adults was gradually decreased with age, and the results were somewhat different according to gender.

• Journal of the Korean Society of Radiology
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• v.9 no.2
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• pp.79-99
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• 2015

Participants of this study were students of radiology who were attending colleges or universities located in Daegu and Gyeongbuk. This researcher conducted a questionnaire survey of those students from Feb. 3rd to 21st, 2014. The findings of the study can be summarized as follows. 1. Concerning the knowledge of radiation exposure management, the respondents' scores were highest in two items, or 'Materials based on lead or concrete may shield X-rays' and 'The sexual gland is very sensitive to radiation' and lowest in the item which says' 'Occupational radiation exposure dose should not exceed 20mSv a year in average on a 5-year period basis'. 2. The participants' scores for the attitudes of radiation exposure management were higher in two items, or 'Health examination should be made regularly in relation to radiation exposure' and 'Those who work within the area of irradiation should wear protective clothes' and lowest in the item which says 'Radiation exposure dose should be regularly measured for the calibration of the radiation system'. 3. For the behaviors of radiation exposure management, the surveyed students showed highest scores in two items, or 'When irradiating the patient, the radiator should be behind the protective barrier(plate)' and 'It is needed to receive the education of radiation exposure management regularly' While, their score for a behavior described in the item saying 'Before using the radiation system, it is needed to check whether the machine works normally.

• The Korean Journal of Nuclear Medicine Technology
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• v.15 no.1
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• pp.75-80
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• 2011

Purpose: Europe and U.S use multi-bed therapy rooms. Hereupon, this study aims to examine the safety when current one-bed therapy rooms in Seoul National University Hospital is changed into two-bed ones. Materials and Methods: This study evaluated external exposure by gamma radiation emitted from other patients and internal and external exposure caused by pollutions from other patients in case that Seoul National University Hospital installs a shielding wall between beds in existing therapy rooms. Results: When internal and external exposure was evaluated to evaluate safety of two-bed hospital rooms, 'isolation amount of patients' 5mSv exposure or below is received according to the Atomic Energy Act. Conclusion: With the increasing number of patients with thyoid cancer, patients using therapy rooms are on the rise. Therefore, improving one-person therapy rooms to two-person ones in line with international trend would increase cost reduction and management efficiency, and patients' alienation and isolation can be reduced to increase healing effects.

• Journal of radiological science and technology
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• v.38 no.4
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• pp.347-353
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• 2015

The purpose of this study is to suggest proper additional filtration by comparisons patient dose and image quality among additional filters in digital chest tomosynthesis (DTS). We measured the effective dose, dose area product (DAP) by changing thickness of Cu, Al and Ni filter to compare image quality by CD curve and SNR, CNR. Cu, Al and Ni exposure dose were similar thickness 0.3 mm, 3 mm and 0.3 mm respectively. The exposure dose using filter was decreased average about 33.1% than non filter. The DAP value of 0.3 mm Ni were decreased 72.9% compared to non filter and the lowest dose among 3 filter. The effective dose of 0.3 mm Ni were decreased 48% compared to 0.102 mSv effective dose of non filter. At the result of comparison of image quality through CD curve there were similar aspect graph among Cu, Al and Ni. SNR was decreased average 19.07%, CNR was average decreased 18.17% using 3 filters. In conclusion, Ni filtration was considered to be most suitable when considered comprehensive thickness, character, sort of filter, dose reduction and image quality evaluation in DTS.

• Radiation Oncology Journal
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• v.11 no.2
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• pp.233-240
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• 1993

Chromosomal aberration analysis, as a basis for biological radiation dosimetry, was performed for radiation dose ranges below 150 cGy. The yield, ratio of lymphocytes with dicentric and/or ring chromosomes, was 0, 0, 0.4, 0.5, 0.6, 0.8, 1.8, 5.5, 8.0, and $18.5\%$ for 0,5, 10, 15, 20, 25, 50, 75, 100 and 150 cGy, respectively. The Qdr, ratio of dicentric and ring chromosomes in total lymphocytes, was 0, 0, 0.004, 0.005, 0.006, 0.009, 0.018, 0.055, 0.084 and 0.207, respectively. The Qdr, ratio of dicentric and ring chromosomes in lymphocytes with aberration, was 1.0 for the radiation doses up to 75 cGy and 1.05 and 1.11 for 100 and 150 cGy, respectively. From the results, it seems possible to estimate radiation dose from Ydr when the exposure is 25 cGy or more. All the 5 radiation workers studied, with exposure much less than 1 mSv per month, had chromosomal aberrations. And acentric fragment pairs, in addition to dicentric and ring chromosomes, showed good dose response relationship and so may be useful for biological dosimetry for low dose radiation.

• Journal of Nuclear Fuel Cycle and Waste Technology(JNFCWT)
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• v.18 no.1
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• pp.103-111
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• 2020

Pulling-type cutting devices, which use a diamond wire saw, have been used generally for cutting concrete structures. In this study, a pushing-type cutting device with a collection cover was developed by overcoming the disadvantages of pulling-type devices. In this device, dry or liquid methods can be selected to cool frictional heat. Operation and leakage tests of the dust generated during the dismantling of a concrete structure were carried out, confirming the suitable operation of the fabricated cutting device; the leakage rate was approximately 1.7%. For a conservative evaluation, the internal dose of workers was estimated in dismantling the core center part of biological shield concrete with a specific activity of 99.5 Bq·g^-1. The committed effective dose per worker was 0.25 mSv. The developed cutting device contributed to reducing radioactive concrete waste and minimizing worker exposure due to its easy installation. Therefore, it can be utilized as a cutting apparatus for dismantling not only reinforced concrete structures but also radioactive biological shield concrete in nuclear power plant decommissioning efforts.

• 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%).

• Journal of Radiation Protection and Research
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• v.39 no.4
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• pp.159-167
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• 2014

In Korea, July 2012, the law as called 'Act on Safety Control of Radioactive Rays Around Living Environment' was implemented to control the consumer product containing Naturally Occurring Radioactive Material (NORM), but, there are no appropriate database and effective dose calculation system. The aim of this study was to develop evaluation technique of the exposure dose with the use of the consumer products containing NORM and to understand the characteristics of the exposed dose according to the radiation type and energy. For the evaluate of exposure dose, the ICRP reference phantom was simulated by the MCNPX code based on Monte Carlo method, and the minimum, medium, maximum energy of alphas, betas, gammas from the representative NORM of Uranium decay series were used as the source term in the simulation. The annual effective doses were calculated by the exposure scenario of the consumer product usage time and position. Short range of the alpha and beta rays are mostly delivered the dose to the skin. On the other hand, the gamma rays mostly delivered the similar dose to all of the organs. The results of the annual effective dose with $1Bq{\cdot}g^{-1}$ radioactive stone-bed and 10% radioactive concentration were employed with the usage time of 7 hours 50 minute per day, the maximum annual effective dose of alphas, betas, gammas were calculated 0.0222, 0.0836, $0.0101mSv{\cdot}y^{-1}$, respectively.