• Journal of Radiation Protection and Research
• /
• v.35 no.1
• /
• pp.34-42
• /
• 2010

With the expanded use of radiation in modern medical practices, the most important issue in regards to efforts to reduce individual exposure dose is quality assurance. Therefore in order to study the present condition of quality assurance, the Gwangju Metropolitan City area was divided into five districts each containing ten hospitals. Four experiments were conducted: a reproducibility experiment for kVp, mA, and examination time (sec) intensity of illumination; half-value layer (HVL) measurement; and beam perpendicularity test matching experiment. The tube voltage reproducibility experiment for all fifty hospitals resulted in a 95.33% passing rate and mA and examination time both resulted in a 77.0% passing rate. The passing rate for intensity of illumination was 86.0% and 52.0% for HVL, which was the lowest passing rate of all four factors. For the beam perpendicularity test matching experiment, generally the central flux is matched to within $1.5^{\circ}$. Of all fifty hospitals 30.0% were beyond $3^{\circ}$. The results of the survey showed that 58% responded that they knew about quality assurance cycle. All fifty respondents stated that they have not received any training in regards to quality assurance at their current place of employment. Although quality assurance is making relative progress, the most urgent issue is awareness of the importance of quality assurance. Therefore, the implementation of professional training focusing on safety management and accurate quality assurance of radiation will reduce the exposure to radiation for radiologists and patients and higher quality imaging using less dosage will also be possible.

• Korean Journal of Environmental Biology
• /
• v.39 no.3
• /
• pp.390-398
• /
• 2021

In this study, the toxicity of chlorothalonil was investigated using survival rate and population growth rate of a marine rotifer, Brachionus plicatilis, typically used in live food in marine aquaculture systems. The survival rate of B. plicatilis was determined after 24 h of exposure to chlorothalonil (0.010-0.156 mg L^-1). Population growth rate of B. plicatilis was calculated after 72 h of exposure to chlorothalonil (0.078-1.250 mg L^-1). The survival rate and population growth rate of B. plicatilis exposed to chlorothalonil in single-dose toxicity assessment showed concentration-dependent reductions. Survival rates of B. plicatilis exposed to chlorothalonil had the following values: NOEC, 0.020mg L^-1; LOEC, 0.039 mg L^-1; and EC₅₀, 0.057 mg L^-1. Population growth rate of B. plicatilis exposed to chlorothalonil had the following values: NOEC, 0.156 mg L^-1; LOEC, 0.313 mg L^-1; and EC₅₀, 0.506 mg L^-1. When the residual concentration of chlorothalonil in the marine coastal area was more than 0.039 mg L^-1, it had a toxic effect on B. plicatilis, a zooplankton. This paper provides toxicity values that can be used as baseline data for organizing environmental standards of chlorothalonil. It also provides insight into toxic effects of chlorothalonil on other non-target organisms.

• Journal of Marine Life Science
• /
• v.5 no.1
• /
• pp.9-16
• /
• 2020

We evaluated the toxic effects of antifouling paint (irgarol and diuron) on the population growth rate (r) of the marine diatom, Skeletonema costatum. The r of S. costatum was determined after 96 hrs of exposure to irgarol (0, 0.31, 0.63, 1.25, 2.5 and 5 ㎍ l^-1) and diuron (0, 7.81, 15.63, 31.25, 62.5 and 125 ㎍ l^-1). It was observed that r in the control (absence of irgarol and diuron) were greater than 0.04, while r in the treatment groups decreased with increasing irgarol and diuron concentrations. Irgarol and diuron reduced r in a dose-dependent manner with significant decreases occurring at concentrations above 0.63 and 15.63 ㎍ l^-1, respectively. The EC₅₀ values of r in irgarol and diuron exposure were 1.09 and 45.45 ㎍ l^-1. No observed effect concentration (NOEC) were 0.31 and 7.81 ㎍ l^-1, the lowest observed effect concentration (LOEC) were 0.63 and 15.63 ㎍ l^-1. This result indicate that a concentration of greater than 0.63 ㎍ l^-1 of irgarol and 15.63 ㎍ l^-1 of diuron in marine ecosystems induced to decreasing r of S. costatum. Also, these toxic values can be useful as a baseline data for the toxic evaluation of irgarol and diuron in marine ecosystems.

• Journal of the Korean Society of Radiology
• /
• v.13 no.1
• /
• pp.81-86
• /
• 2019

In X-ray image, the role of filtration through the filter is to reduce the exposure of the patient by using photon which is useful in formation of the image, and at the same time, enhance the contrast of the image. During interaction between photon and object, low energy X-rays are absorbed from the site of a few cm of the first patient's tissue, and high energy X-rays are the one which form the image. Therefore, the radiation filter absorbs low energy X-ray in order to lower the exposure of the patient and improve the quality of the image. The purpose of this study is to compare the effect on the image quality by differences of added filter through simulation image and actual radiation image. For that purpose, we used Geant4 Application for Tomographic Emission (GATE) as a tool for Monte Carlo simulation. We set actual size, shape and material of Polymethylmethacrylate (PMMA) Phantom on GATE and differentiated the parameter of added filter. Also, we took image of PMMA phantom with same parameter of added filter by digital radiography (DR). Than we performed contrast-to-noise ratio (CNR) evaluation on both simulation image and actual DR image by Image J. Finally, we observed the effect on image quality due to different thickness of added filter, and compared two images' CNR evaluation's transitions of change. The result of this experiment showed decreasing in the progress of CNR on both DR and simulation image. It is ultimately caused by decreasing in contrast on image. In theory, contrast decrease with kVp increased. Given that condition, this study found out that filter makes not only decreasing total dose by absorbing low energy of X-ray, but also increasing average energy of X-ray.

• The Korean Journal of Pesticide Science
• /
• v.17 no.4
• /
• pp.350-358
• /
• 2013

Both 13-week and 1-year studies in dog were required for pesticide registration in domestic pesticide control authority. It is raising issue up whether to request 1-year dog study of pesticides using non-food crop. So at this investigation, relevant toxicity test to establish acceptable daily intake (ADI), target organs, difference of no-observed adverse-effect levels (NOAELs) in 13-week and 1-year of 166 active ingredients are analyzed. The data were evaluated to determine if the 13-week dog study and the long term studies in two rodent species (mice and rats) without 1-year dog study were sufficient for the identification of NOAELs and lowest observed adverse effect levels (LOAELs) for the derivation of ADI. Toxicity end points and dose response data from 13 week and 1-year studies were compared. The analysis showed that 68 ADIs of the 166 pesticides were established from dog studies. Major target organs of dog studies were liver in 49 cases, body weight change in 21 cases, cholinesterase inhibition in 16 cases, and alteration in hematology in 14 cases. Similarity of target organ in 13-week and 1-year was 73%. 22 of 40 pesticides had similar critical effects regardless of duration and had NOAELs within a difference of 1.5-fold of each other. For the remaining 18 pesticides, 14 items had lower NOAELs in the 1-year study than 13-week study primarily due to dose selection and spacing. In only 10% of the cases were additional toxic effects identified in the 1-year study that were not observed in the 13-week study.

• Journal of the Korean Society of Radiology
• /
• v.9 no.4
• /
• pp.205-211
• /
• 2015

At a recent medical imaging technology, the major issue of X-ray diagnosis in breast cancer is the early detection of breast cancer and low patient's exposure dose. As one of studies to acquire a monochromatic X-ray, Technologies using multilayer mirror had been preceded. However, a uniform multilayer mirror that consists of uniform thin-film thickness can acquire a monochromatic X-ray only in the partial area corresponds to angle of incidence of white X-ray, so there are limits for X-ray imaging technology applications. In this study, we designed laterally graded multilayer mirror(below GML) that reflects same monochromatic X-ray over the entire area of thin-film mirror, which have the the thickness of the linear gradient that correspond to angle of incidence of white X-ray. By using ion-beam sputtering system added the mask control system we fabricated a GML which has size of $100{\times}100mm^2$. The GML is designed to achieve the monochromatic X-ray of 17.5kev energy and has thin-film thickness change from 4.62nm to 6.57nm(3.87nm at center). It reflects the monochromatic X-ray with reflectivity of more than 60 percent, FWHM of below 2.6keV and X-ray beam width of about 3mm. The monochromatic X-ray corresponded to 17.5keV using GML would have wide application in development of mammography system with high contrast and low dose.

• Journal of Korean Academy of Oral and Maxillofacial Radiology
• /
• v.20 no.2
• /
• pp.253-264
• /
• 1990

The purpose of this study was to estimate the distribution of absorbed doses of each important organs of head and neck region in panoramic radiography. Radiation dosimetry at internal anatomic sites and skin surfaces of phantom (RT-210 Humanoid Head & Neck Section/sup R/) was performed with lithium fluoride (TLD-100/sup R/) thermoluminescent dosimeters according to change of kilovoltage (65kVp, 75kVp and 85kVp) with 4 miliamperage and 20 second exposure time. The results obtained were as follows; Radiation absorbed doses of internal anatomic sites were presented the highest doses of 1.04 mGy, 1.065 mGy and 2.09 mGy in nasopharynx, relatively high doses of 0.525 mGy, 0.59 mGy and 1.108 mGy in deep lobe of parotid gland, 0.481 mGy, 0.68 mGy and 1.191 mGy in submandibular gland. But there were comparatively low doses of 0.172 mGy and 0.128 mGy in eyes and thyroid gland that absorbed dose was estimated at 85kVp. Radiation absorbed doses of skin surfaces were presented the highest doses of 1. 263 mGy, 1.538 mGy and 2.952 mGy in back side of first cervical vertebra and relatively high doses of 0.267 mGy, 0.401 mGy and 0.481 mGy in parotid gland. But there were comparatively low doses of 0.057 mGy, 0.068 mGy and 0.081 mGy in philtrum and 0.059 mGy in middle portion of chin that absorbed dose was estimated at 85kVp. According to increase of kilovoltage, the radiation absorbed doses were increased 1.1 times when kilovolt age changes from 65kVp to 75kVp and 1.9 times when kilovolt age changes from 75kVp to 85kVp at internal anatomic sites. According to increase of kilovoltage, the radiation absorbed doses were increased 1.3 times when kilovolt age changes from 65kVp to 75kVp and 1.6 times when kilovoltage changes from 75kVp to 85kVp at skin surfaces.

• The Journal of Internal Korean Medicine
• /
• v.19 no.1
• /
• pp.409-427
• /
• 1998

Insamjungchuntang has been used in Korea for many centuries as a treatment for respiratory disease. The effect of Insamjungchuntang on tracheal smooth muscle is not known. The purpose of the present study is to determine the effect of Insamjungchuntang on histamine and acetylcholine induced tracheal smooth muscle contraction in rats and guinea pigs. Guinea pig (500 g, male) and Sprague Dawley rats (200 g, male) were killed by $CO_2$ exposure and a segment (8-10 mm) of the thoracic trachea from each rat and guinea pig was cut into equal segments and mounted 'in pairs' in a tissue bath. Contractile force was measured with force displacement transducers under 0.5 g loading tension. The dose of histamine (His) and acetylcholine (Ach) which evoked 50% of maximal response $(ED_{50})$ was obtained from cumulative dose response curves for histamine and acetylcholine$(10^{-7}{\sim}10^{-4}\;M)$. Contractions evoked by His ($ED_{50}$) and Ach $(ED_{50})$ were inhibited significantly by Insamjungchuntang. In guinea pig tracheal smooth muscle, the mean percent inhibition of acetylcholine induced contraction was $38.58\(p<0.05)\;after\;10{\mu}l/ml$ Insamjungchuntang, $90.75\(p<0.01)\;after\;30{\mu}l/ml$. Insamjungchuntang and $133.17\(p<0.01)\;after\;100{\mu}l/ml$ Insamjungchuntang. In rat tracheal smooth muscle, the mean percent inhibition of acetylcholine induced contraction was $10.0\(p<0.05)\;after\;10{\mu}l/ml$ Insamjungchuntang, $80.71\(p<0.01)\;after\;30{\mu}/ml$ Insamjungchuntang and $118.29\(p<0.01)\;after\;100{\mu}l/ml$ Insamjungchuntang. Also, in guinea pig tracheal smooth muscle, the mean percent inhibition of histamine induced contraction was $45.5\(p<0.01)\;after\;10{\mu}l/ml$ lnsamjungchuntang, and $93.17\(p<0.01)\;after\;30{\mu}l/ml$. lnsamjungchuntang $134.50\(p<0.01)\;after\;100{\mu}l/ml$ Insamjungchuntang. In rat tracheal smooth muscle, the mean percent inhibition of histamine induced contraction was $37.83\(p<0.01)\;after\;10{\mu}l/ml$ lnsamjungchuntang, $90.5\(p<0.01)\;after\;30{\mu}l/ml$ Insamjungchuntang and $135.17\(p<0.01)\;after\;100{\mu}l/ml$ Insamjungchuntang. Propranolol $(10^{-7}\;M)$ slightly but significantly attenuated the inhibitory effects of Insamjungchuntang. Following treatment with propranolol, the mean percent inhibition caused by $100{\mu}l/ml$. Insamjungchuntang fell to 46.42% in guinea pig induced by acetylcholine contraction and by $100{\mu}l/ml$ Insamjungchuntang fell to 5.43% (p<0.05) in rat induced by acetylcholine contraction and the mean percent inhibition caused by $100{\mu}l/ml$ Insamjungchuntang fell to 49.0% in guinea pig induced by histamine contraction and by $100{\mu}l/ml$ Insamjungchuntang fell to 48.6% (p<0.05) in rat induced by histamine contraction. Indomethacin and methylene blue $(10^{-7}\;M)$ did not significantly alter the inhibitory effect of lnsamjungchuntang. Also, I could find the effects of lnsamjungchuntang and Insamjungchuntanggamorphine on the tracheal smooth muscle in guinea pig and rat did not change significantly. These results indicate that Insamjungchuntang can relax histamine and acetylcholine-induced contraction of guinea pig and rat tracheal smooth muscle, and that this inhibition involves sympathetic effects.

• Radiation Oncology Journal
• /
• v.12 no.1
• /
• pp.1-8
• /
• 1994

When cells are exposed to low doses of a mutagenic or clastogenic agents. they often become less sensitive to the effects of a higher dose administered subsequently. Such adaptive responses were first described in Escherichia coli and mammalian cells to low doses of an alkylating agent. Since most of the studies have been carried out with human lymphocytes, it is urgently necessary to study this effect in different cellular systems. Its relation with inherent cellular radiosensitivity and underlying mechanism also remain to be answered. In this study, adaptive response by 1 cGy of gamma rays was investigated in three human lymphoblastoid cell lines which were derived from ataxia telangiectasia homozygote, ataxia telangiectasia heterozygote, and normal individual. Experiments were carried out by delivering 1 cGy followed by 50 cGy of gamma radiation and chromatid breaks were scored as an endpoint. The results indicate that prior exposure to 1 cGy of gamma rays reduces the number of chromatid breaks induced by subsequent higher dose (50 cGy), The expression of this adaptive response was similar among three cell lines despite of their different radiosensitivity. When 3-aminobenzamide, an inhibitor of poly (ADP-ribose) polymerase, was added after 50 cGy, adaptive responses were abolished in all the tested cell lines. Therefore it is suggested that the adaptive response can be observed in human lymphoblastoid cell lines, which was first documented through this study. The expression of adaptive response was similar among the cell lines regardless of their radiosensitivity. The elimination of the adaptive response by 3-aminobenzamide is consistent with the proposal that this adaptive response is the result of the induction of a certain chromosomal repair mechanism.

• Journal of radiological science and technology
• /
• v.39 no.3
• /
• pp.377-384
• /
• 2016

This is a study on the optimized dispensing of the auto dispenser used for the purpose of reducing the exposure dose and accurate radiation dose of radioisotope with regard to the PET/CT practitioners. The research method was to find the optimized dispensing method through evaluating the results according to the syringe type, dispensing rate, and vial pressure and through the application of corrected values. As a result of this study, 9.38 mCi has been dispensed on average in the case of 5 ml syringe, and the reproducibility close to 10 mCi was shown at the dispense of 9.55 mCi in the case of 3 ml syringe. In the evaluation according to the dispensing rate, the quantity of radioisotope close to 10 mCi was dispensed at the rate of 5 mm/min when the measurement was carried out by increasing the rate by 5 mm/min units in the order of 5, 10, 15 and 20 mm/min. In the evaluation result according to the vial pressure before/after the use of Needle filter, it was measured to be 9.53 mCi before use and 9.84 mCi after use confirming that the dispensing after using Needle filter showed the optimal value. In addition, in the evaluation of radioactivity before/after the application of corrected values according to the increase in dispense frequency, it was measured 9.53 mCi before correction and 10.07 mCi after correction confirming that the value with correction applied was closer to the quantitative value. Thus, a good optimized method was confirmed to use a 3 ml syringe with dispensing rate of 5 mm/min, to use a Needle filter at dispensing, and to set the corrected value of [$y=0.097{\times}x$] according to the dispensing frequency of equipment.