• Journal of the Korean Society of Radiology
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• v.15 no.6
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• pp.803-811
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• 2021

In this study, the exposure amount of IASCC test worker was evaluated by applying the process simulation technology. Using DELMIA Version 5, a commercial process simulation code, IASCC test facility, hot cells, and workers were prepared, and IASCC test activities were implemented, and the cumulative exposure of workers passing through the dose-distributed space could be evaluated through user coding. In order to simulate behavior of workers, human manikins with a degree of freedom of 200 or more imitating the human musculoskeletal system were applied. In order to calculate the worker's exposure, the coordinates, start time, and retention period for each posture were extracted by accessing the sub-information of the human manikin task, and the cumulative exposure was calculated by multiplying the spatial dose value by the posture retention time. The spatial dose for the exposure evaluation was calculated using MCNP6 Version 1.0, and the calculated spatial dose was embedded into the process simulation domain. As a result of comparing and analyzing the results of exposure evaluation by process simulation and typical exposure evaluation, the annual exposure to daily test work in the regular entrance was predicted at similar levels, 0.388 mSv/year and 1.334 mSv/year, respectively. Exposure assessment was also performed on special tasks performed in areas with high spatial doses, and tasks with high exposure could be easily identified, and work improvement plans could be derived intuitively through human manikin posture and spatial dose visualization of the tasks.

• Radiation Oncology Journal
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• v.20 no.1
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• pp.41-52
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• 2002

Purpose : 3D conformal radiotherapy, the optimum dose delivered to the tumor and provided the risk of normal tissue unless marginal miss, was restricted by organ motion. For tumors in the thorax and abdomen, the planning target volume (PTV) is decided including the margin for movement of tumor volumes during treatment due to patients breathing. We designed the respiratory gating radiotherapy device (RGRD) for using during CT simulation, dose planning and beam delivery at identical breathing period conditions. Using RGRD, reducing the treatment margin for organ (thorax or abdomen) motion due to breathing and improve dose distribution for 3D conformal radiotherapy. Materials and Methods : The internal organ motion data for lung cancer patients were obtained by examining the diaphragm in the supine position to find the position dependency. We made a respiratory gating radiotherapy device (RGRD) that is composed of a strip band, drug sensor, micro switch, and a connected on-off switch in a LINAC control box. During same breathing period by RGRD, spiral CT scan, virtual simulation, and 3D dose planing for lung cancer patients were peformed, without an extended PTV margin for free breathing, and then the dose was delivered at the same positions. We calculated effective volumes and normal tissue complication probabilities (NTCP) using dose volume histograms for normal lung, and analyzed changes in doses associated with selected NTCP levels and tumor control probabilities (TCP) at these new dose levels. The effects of 3D conformal radiotherapy by RGRD were evaluated with DVH (Dose Volume Histogram), TCP, NTCP and dose statistics. Results : The average movement of a diaphragm was 1.5 cm in the supine position when patients breathed freely. Depending on the location of the tumor, the magnitude of the PTV margin needs to be extended from 1 cm to 3 cm, which can greatly increase normal tissue irradiation, and hence, results in increase of the normal tissue complications probabiliy. Simple and precise RGRD is very easy to setup on patients and is sensitive to length variation (+2 mm), it also delivers on-off information to patients and the LINAC machine. We evaluated the treatment plans of patients who had received conformal partial organ lung irradiation for the treatment of thorax malignancies. Using RGRD, the PTV margin by free breathing can be reduced about 2 cm for moving organs by breathing. TCP values are almost the same values $(4\~5\%\;increased)$ for lung cancer regardless of increasing the PTV margin to 2.0 cm but NTCP values are rapidly increased $(50\~70\%\;increased)$ for upon extending PTV margins by 2.0 cm. Conclusion : Internal organ motion due to breathing can be reduced effectively using our simple RGRD. This method can be used in clinical treatments to reduce organ motion induced margin, thereby reducing normal tissue irradiation. Using treatment planning software, the dose to normal tissues was analyzed by comparing dose statistics with and without RGRD. Potential benefits of radiotherapy derived from reduction or elimination of planning target volume (PTV) margins associated with patient breathing through the evaluation of the lung cancer patients treated with 3D conformal radiotherapy.

• 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 Radiation Protection and Research
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• v.39 no.1
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• pp.21-29
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• 2014

A new cold neutron triple-axis spectrometer (Cold-TAS) was recently constructed at the 30 MWth research reactor, HANARO. The spectrometer, which is composed of neutron optical components and radiation shield, required a redesign of the segmented monochromator shield due to the lack of adequate support of its weight. To shed some weight, lowering the height of the segmented shield was suggested while adding more radiation shield to the top cover of the monochromator chamber. To investigate the radiological effect of such change, we performed MCNPX simulations of a few different configurations of the Cold-TAS monochromator shield and obtained neutron and photon intensities at 5 reference points just outside the shield. Reducing the 35% of the height of the segmented shield and locating lead 10 cm from the bottom of the top cover made of polyethylene was shown to perform just as well as the original configuration as radiation shield excepting gamma flux at two points. Using gamma map by MCNPX, it was checked that is distribution of gamma. Increased flux had direction to the top and it had longer distance from top of segmented shield. However, because of reducing the 35% of the height, height of dissipated gamma was lower than original geometry. Reducing the 35% of the height of the segmented shield and locating lead 10cm from the bottom of the top cover was selected. After changing geometry, radiation dose was measured by TLD for confirming tester's safety at any condition. Neutron(0.21 ${\mu}Svhr^{-1}$) and gamma(3.69 ${\mu}Svhr^{-1}$) radiation dose were satisfied standard(6.25 ${\mu}Svhr^{-1}$).

• Radiation Oncology Journal
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• v.19 no.1
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• pp.74-80
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• 2001

Purpose : Irradiation cones by using backscatter electrons are made for the treatment of superficial small lesions of skin, oral cavity, and rectum where a significant dose gradient and maximum surface dose is desired. Methods and Materials : Backscatter electrons are produced from the primary electron beams from the linear accelerators. The design consists of a cylindrical cone that has a thick circular plate of high atomic number medium (Pb or Cu) attached to the distal end, and the plate can be adjusted the reflected angle. Primary electrons strike the metal plate perpendicularly and produce backscatter electrons that reflect through the lateral hole for treatment. Using film and a parallel plate ion chamber, backscatter electron dose characteristics are measured. Results : The depth dose characteristic of the backscatter electron is very similar to that of the hard x-ray beam that is commonly used for the intracavitary and superficial lesions. The basckscatter electron energy is nearly constant and effectively about 1.5 MeV from the clinical megavoltage beams. The backscatter electron dose rate of $35\~85\;cGy/min$ could be achieved from modern accelerators without any modification. and the depth in water of $50\%$ depth dose from backscatter electron located at 6mm for $45^{\circ}$ angled lead scatter. The beam flatness is dependent on the slit size and the depth of treatment, but is satisfactory to treat small lesions. Conclusions : The measured data for backscatter electron energy, depth dose flatness dose rate and absolute dose indicates that the backscatter electrons are suitable for clinical use.

• The Journal of Korean Society for Radiation Therapy
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• v.26 no.1
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• pp.51-57
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• 2014

Purpose : In the case of treating pancreatic cancer, the importance is put on the spread of dose. Changes take place in duodenum in accordance with respiration. Thus, in this paper, I am going to trace the positioning of duodenum and the changes in bulks of body per dose by scanning the patients' Kilovoltage Cone-Beam CT using the hospital equipped CT-on rail System. Materials and Methods : Seeing three patients, I have acquired KVCBCT by using CT-on rail System and spotted the change in positioning at duodenum after comparing with the preliminary image of treatment plan by using SYNGO Software. Then, I followed the change in the bulk of duodenum and analyzed the changes in bulks of body on the same dose by transmitting the acquired KVCBCT into Pinnacle, a treatment plan system. Results : The changes in the positioning shall be as set forth like this: 1.2cm, 1.0cm in Left-Right Direction, 0cm, 0.8cm in Craniocaudal Direction, 0.1cm, and 1.0cm in Anterior-Posterior Direction. Patient number one showed that his bulks in body had increased by maximum 460%, minimum 120%, the bulks in patient number two had increased bymaximum 490%, minimum 160%, and the bulks of patient number three had increased by maximum 150%. But Minimum volume decreased 30%. Patient number one showed only a little bit of change at first when compared with the preliminary treatment plan. However, the dose increased the bulks in the patient's body: $V_{10}$ 118%, $V_{20}$ 117%, $V_{30}$ 400%, and $V_{40}$ 480% Conclusion : In treating patients with radiation therapy using 3D-CRT, the dose amount penetrated into duodenum needs to be minimized by planning appropriate treatment beforehand. In order to establish an appropriate treatment plan it is required to comprehend the changes at positioning of the duodenum by respiration and predict the changes in the bulks of duodenum by setting precise Planning Target Volume.

• Journal of the Korean Society of Food Science and Nutrition
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• v.28 no.4
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• pp.882-885
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• 1999

Along with the increasing demands for food irradiation technology, proper detection methods for controlling irradiated foods are required. Dried vegetable(chunggyungchae), which is permitted to be irradiated in Korea, was subjected to a detection study by ESR spectroscopy. Pre established threshold value was successfully applicable to the detection of 50 coded unknown samples of dried clean vege tables, both nonirradiated and electron beam irradiated. Three calibration curves obtained from the samples irradiated at 2.5~15 kGy were not practically adopted to estimate actual absorbed doses ranging from 4 to 7 kGy.

• The Korean Journal of Nuclear Medicine Technology
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• v.12 no.3
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• pp.157-170
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• 2008

Purpose: This prospective study was conducted to reveal the haematological index change by low level radiation exposure in radiological environment our hospital workers. Materials and Method: We gathered the cumulative dose by Thermoluminenscent Dosimeters (TLD) over 9-yr period and examined hematological index counts change (RBC, Hb, Platelet, WBC, Monocyte, Lymphocyte, Neutrophilic, Basophilic, Eosinophilic) both occupational workers and controls. Of a total 370 occupational workers and 335 controls were compared. Results: This analysis has led to the following general observations 1) The average cumulative dose in male and female were $9.65{\pm}15.2\;mSv$, $4.82{\pm}5.55\;mSv$ respectively. 2) In both male and female, there were very low relationship between occupation period and cumulative dose (r< ${\pm}0.25$). 3) Occupation period was more increased, in male, WBC counts decreased and increased workers, RBC counts decreased workers were more than controls group (p<0.05). In female, WBC counts decreased and increased workers and W-eosino counts decreased workers were more than controls group (p<0.01). 4) Cumulative dose was more increased, in male, W-Lympho counts decreased workers and Platelet counts deceased workers were more than controls group (p<0.05). In female, W-lympho counts decreased workers and RBC counts decreased workers were more than controls group (p<0.05). Conclusions: We can find some kinds of blood index abnormal distribution in occupational radiation workers by comparing with controls. Occupational workers cannot avoid radiation exposure, in spite of the control it. Actually low level radiation adverse effect occurred not dose but probability. So workers must always try to reduce exposure by ourselves, furthermore as long as possible the government should provide rapidly that national system on radiation control for worker's health.

• Journal of the Korean Society of Radiology
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• v.12 no.3
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• pp.289-295
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• 2018

Most diagnostic devices in the medical field use X-ray sources, which emit energy spectra. In radiological diagnosis, the quantitative and qualitative analyses of X-rays are essential for maintaining the image quality and minimizing the radiation dose to patients. This work aims to obtain the X-ray energy spectra used in diagnostic imaging by Monte Carlo simulation. Various X-ray spectra are simulated using a Monte Carlo simulation tool. These spectra are then compared to the reference data obtained with a tungsten anode spectral model using the interpolating polynomial (TASMIP) code. The X-ray tube voltages used are 50, 60, 80, 100, and 110 kV, respectively. CdTe and a-Se detector are used as the detectors for obtaining the X-ray spectra. Simulation results demonstrate that the various X-ray spectra are well matched with the reference data. Based on the simulation results, an appropriate X-ray spectrum, in accordance with the tube voltage, can be selected when generating an image for diagnostic imaging. The dose to be delivered to the patient can be predicted prior to examination in the diagnostic field.

• Analytical Science and Technology
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• v.27 no.6
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• pp.292-299
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• 2014

Iopromide is an X-ray contrast agent that has been detected frequently with high concentration level in surface waters. Structural characterization of degradation products and measurement of degradation efficiency of iopromide by an electron beam irradiation were performed. For the fortified sample with iopromide, electron beam irradiation (UELV-10-10S, klysotrn, 10 MeV, 1 mA and 10 kW) was performed. The chemical structures of I_D_665 and I_D_663, which are degradation products of iopromide, were proposed by interpretation of mass spectra and chromatograms by LC/ESI-MS/MS. The mass fragmentation pathways of mass spectra in tandem mass spectrometry were also proposed. Iopromide was degraded 30.5~98.4% at dose of 0.3~5 kGy, and 97.8~30% in the concentration range $0.5{\sim}100{\mu}g/kg$ at electron beam dose of 0.3 kGy, respectively. Thus, increased degradation efficiency of iopromide by electron beam irradiation was observed with a higher dose of electron beam and lower concentration.