• Polymer(Korea)
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• v.32 no.6
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• pp.598-602
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• 2008

In this study we prepared crosslinked separators with the improved thermal stability by irradiating a commercial polyethylene (PE) separator for lithium secondary battery with an electron beam, and the thermal and mechanical properties of the prepared separators were evaluated as a function of the absorption dose. The thermal shrinkage of electron beam irradiated separator was decreased with increasing absorption dose. As a result of the shutdown behavior using an AC impedance, it was observed that the irradiated separator had the better shutdown function than the unirradiated separator. The modulus of the irradiated separator was enhanced as the absorption dose was increased, while the tensile strength and the break elongation of the irradiated separator were decreased.

• The Journal of Korean Society for Radiation Therapy
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• v.16 no.2
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• pp.69-79
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• 2004

In the process of photon treatments, linear accelerators with energies higher than 10 MV produce neutrons through the (${\gamma}$, n) interactions with the composite materials of the linac head md these materials further produce the induced radiations. We investigate the possible risks from these induced radiations especially in the wedge filters to the radiation workers. Wedge filters are used to modify the isodose profiles in the radiation treatment using the linear accelerator and always be handled by the radiation workers. For the background radiation, we measured the radiation in both the waiting room and the outside of the building for two hospitals, S and H. The results of S hospital were $0.11\;{\mu}Sv/hr$ and $0.10\;{\mu}Sv/hr$ for waiting room and outside respectively, and in the case of H hospital, they were $0.12\;{\mu}Sv/hr$ and $0.11\;{\mu}Sv/hr$. Using a survey meter, we measured the radiation from wedge filters inserted in 10 MV and 15 MV Siemens linear accelerators. The time series measurements were done in ${\sim}1$ minutes after exposure of 5 Gy of monitor units for the field size of $25{\times}25cm^2$. The starting value of 10 MV machine was about $3.26\;{\mu}Sv/hr$, which was three times higher than that of 10 MV. The measured radiation was from $^{28}Al$ and $^{53}Fe$ with a half life of 3.5 min. If the treatment patients are $20{\sim}50$ per day and the number of process of wedge filter change per patient is one or two, the annual dose equivalent is $0.08{\sim}0.4\;mSv$ for 10 MV, and $0.27{\sim}1.36\;mSv$ for 15 MV, which are in the range of dose equivalent limits of radiation workers.

• Journal of the Korean Society of Radiology
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• v.12 no.5
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• pp.583-592
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• 2018

In this study, plans to apply 3D conformal radiotherapy, intensity modulated radiotherapy, and volumetric intensity modulated arc radiotherapy to esophageal cancer radiotherapy were compared. In particular, arc therapy was applied to reduce irradiated volume and spread of low-dose during intensity modulated radiation therapy and volumetric intensity modulated arc radiotherapy by limiting part of irradiated angle, in order to compare target doses and dose for surrounding normal tissues of the two methods and those of 3D conformal radiotherapy. No significant difference in target dose was found among the three methods. The 5 Gy volume(V5) of the lung showed 56.53% of conformal radiotherapy, 52.03% of intensity modulated radiotherapy, and 47.84% of volumetric modulated arc therapy(CRT-IMRT p=0.035, CRT-VMAT p<0.001, IMRT-VMAT p<0.001). The 10 Gy volume(V10) showed a significant difference in conformal radiotherapy 35.12%, intensity modulated radiotherapy 34.04%, and volumetric modulated arc radiotherapy 33.28%, showing significant difference in intensity modulated radiotherapy(p=0.018), volumetric modulated arc therapy(p=0.035), no significant difference in dose was found at 20 Gy volume. The mean dose and 20 Gy volume of the heart were not significantly different according to the treatment plan, but the 30 and 40 Gy volumes were 37.16% and 22.46% in the volumetric modulated arc radiotherapy, showing significant differences(p=0.028) in comparison with conformal radiotherapy. It is believed that, by limiting part of the irradiated angle during intensity modulated radiotherapy and volumetric intensity modulated arc radiotherapy, the irradiated volume and, thereby, the 5-10 Gy area and toxicity of the lung can be reduced while maintaining dose distribution of the target dose.

• Journal of the Korean Society of Radiology
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• v.8 no.2
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• pp.75-79
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• 2014

The aim of this retrospective research was to investigate the influence of the patient's arm position on radiation dose and scanning during CT. Chest CT image created image degradation, artifact and overdose to the patient due to the difference of the chest thickness. Therefore, the patient's arm should up position during the CT chest examination. In 2012, 1,642 patients underwent chest CT examination in Seoul K hospital. 118 chest CT examination performed hands down position. The average DLP value of the CT chest arm up examination was 275 $mGy{\cdot}cm$. The average DLP value of the CT chest arm down examination was 312.46 $mGy{\cdot}cm$. In the retrospective study with same patient, The average DLP value of the CT chest examination arm up vigorously was 267.5 $mGy{\cdot}cm$. The average DLP value of the CT chest arm down examination was 307.5 $mGy{\cdot}cm$. Chest CT scan without raising arm created linear artifact due to the lack of X-ray photons which is the thickest part of the human body of shoulder area. In conclusion, arm positioning patients' arms above the shoulders at CT of the chest increases image quality and substantially reduces effective radiation dose.

• Journal of Conservation Science
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• v.34 no.6
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• pp.481-492
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• 2018

We conducted TL/OSL dating for the earthenware kilns in the Bongsan-ri archaeological site, Osong, which was occupied from the late nineteenth to the late twentieth century. With the SAR-TL/OSL method, paleodose was determined from the equivalent dose during the burial period($ED_{burial}$), the background dose($ED_{BG}$), the fading correction factor(f), and the overestimation correction factor(C). The annual dose rates and their provenance were evaluated from the measurement of natural radionuclides $^{238}U$, $^{232}Th$, and $^{40}K$. Because the comprehensive absolute age was provided by combining the resulting TL/OSL and radiocarbon data, we concluded that, for the absolute chronology of a modern archaeological site, TL/OSL dating and radiocarbon dating must be carried out together and summed. The construction and occupation of earthenware kilns in the Bongsan-ri site had changed from stage I (No.5, 6 kilns), to stage II (No.1, 2, 3 kilns), to stage III (No.4) in chronological order. When Bayesian statistics were applied, we found that the absolute ages of occupation for stages I, II, and III correspond to AD $1910{\pm}23$, AD $1970{\pm}10$, and AD $1987{\pm}4$. These results were in good agreement with the archaeological context or chronology.

• Proceedings of the KIEE Conference
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• 2002.07d
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• pp.2285-2288
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• 2002

Recently, electronic personal dosimeters based upon silicon PIN photodiode or miniature GM tube were developed and have attracted a lot of attention because of the advantages of their nature such as indication of dose rate and the cumulative dose, and facilitation of record keeping. In this paper, we have developed a high-sensitivity electronic personal dosimeter with silicon PIN photodiode. The electronic personal dosimeter is constructed with silicon PIN photodiode, preamplifier, and shaping amplifier. To show the effectiveness of electronic personal dosimeter, we conducted nuclear radiation experiments using $\gamma$-ray Ba-133, Cs-137, and Co-60. The electronic personal dosimeter have a good linearity on $\gamma$-ray energy and activity.

• Proceedings of the KIEE Conference
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• 2003.11c
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• pp.540-543
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• 2003

This paper presents design and manufacture of RF type non-contact radiological dosage measuring device. It also concerns on the broad out-line and the ways of improvement about RF type non-contact radiation measuring device. Measuring radiological dosage with non-contact RF, the stability and efficiency of the measure have been improved by reforming constant current circuit. Furthermore, applying communication protocol in process makes it possible to achieve faster and more accurate communication than old circuit. On the base of those, RF type non-contact radiological dosage measuring device which consists of radiological dosage measuring module and Reader module has been designed and manufactured. While testing communication against embodied device, the possibility of the field application could be confirmed.

• The Korean Journal of Nuclear Medicine Technology
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• v.17 no.2
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• pp.15-24
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• 2013

Purpose: With the demand of SPECT/CT increasing, the interest in complex diagnostic information of CT is rising along with the expansion of various studies on potential performance value. But the study on reduction of exposure dose generated by CT is not being conducted enough. Therefore, in this study, the goal is to identify how much dose reduction exists when performing the extremity bone SPECT/CT using the flat-panel CT. Materials and Methods: The extremity bone SPECT/CT was performed with two equipments -BrightView XCT (Philips Healthcare, Cleveland, USA) and Brilliance 16 CT (Philips Healthcare, Cleveland, USA)-to identify the exposed dose and image quality resulted by changing scan parameter (mAs) applying for both equipment respectively. The noise value of image and spatial resolution were measured with AAPM CT phantom. Tube voltage (kVp) was fixed to 120 kVp, tube current (mAs) calculated at different mA (20, 30, 40, 50, 60, 70, 80) was applied to both equipments respectively. DLP (dose length product) were calculated at the same distance at respective mAs. Also, we acquired images and % contrast with NEMA IEC body phantom to confirm the effect on image. The output of statistics was analyzed by SPSS ver.18. Results: Regarding AAPM phantom, the noise decreased as the tube current (mAs) increased and flat-panel had less noise than Helical CT. This difference increased at lower dose exposure. As to the evaluation of spatial resolution, we can differentiate the space up to 0.75 mm with both equipments. With scan parameter (mA) growing, the value of DLP increased up to 54-216 mGy cm at flat-panel CT and up to 177-709 mGy cm at Helical CT. Regarding NEMA IEC body phantom, same sphere with varied parameter (mA) shows that similar results. Conclusion: There is no significant differences of image quality in both flat-panel and Helical CT when the scan parameter (mA) is changed respectively. Moreover, we can identify the reduction of exposure dose and confirm %contrast analysis value with maintaining image quality. Therefore, at the extremity bone SPECT/CT requiring high spital resolution without the wide ROI, the flat-panel CT is considered to be more useful and it expected to result in the similar image quality with lower exposure dose compared to Helical CT. Additionally, through this study, we expect to help the reduction of the unnecessary exposure dose.

• The Korean Journal of Nuclear Medicine Technology
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• v.17 no.2
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• pp.59-66
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• 2013

Purpose: Recently, there is an increase of the number of hospitals using auto dispenser to reduce occupational radiation exposure when drawing up of the $^{18}F-FDG$ dose (5.18 MBq/kg) in a syringe from the dramatic high activity of $^{18}F-FDG$ multidose vial. The aim of this study is to confirm that using auto dispenser actually reduces the radiation exposure for technologists. Also we analyzed the reproducibility of auto dispenser to find optimized dispensing method for the device. Materials and Methods: We conducted three experiments. Comparison of radiation exposure on chest and hands: The chest and hands exposure dose received by technologists during the injection were measured by electronic personal dosimeter (EPD) and ring TLD respectively. Reproducibility of dispensed volume: We draw up the normal saline into 5 and 2 mL syringe using auto dispenser by changing the volume from 1 to 15 mm for 5 times in the same setting of the volume. The weight of 5 normal saline dispensed from the device at same volume was measured using micro balance and calculated standard deviation and coefficient of variation. Reproducibility of dispensed radioactivity: We dispensed 362.6 $MBq{\pm}10%$ of $^{18}F-FDG$ in 5 and 2 mL syringes from the multidose vial of different specific activity. In the same setting of volume, we repeated dispensing for 4 times and compared standard deviation and coefficient of variation of radioactivity between 5 syringes. Results: There was significant difference in the average of chest exposure dose according to the dispensing methods (P<0.05). Also, when dispensing $^{18}F-FDG$ in manual method, exposure dose was 11.5 times higher in right hand and 4.8 times higher in left hand than in auto method. In the result of reproducibility of dispensed volume, standard deviation and coefficient of variation shows decline as the dispensing volume increases. As a result of reproducibility of dispensed radioactivity, standard deviation and coefficient of variation increases as the specific activity increases. Conclusion: We approved that the occupational radiation exposure dose of technologists were reduced when dispensing $^{18}F-FDG$ using auto dose dispenser. Secondly, using small syringes helps to increase reproducibility of auto dose dispense. And also, if you lower the specific activity of $^{18}F-FDG$ in multidose vial below 915-1,020 MBq/mL, you can use auto dispenser more effectively keeping the coefficient of variation lower than 10%.

• Applied Chemistry for Engineering
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• v.10 no.6
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• pp.838-842
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• 1999

In order to reclaim the effluent discharged from sewage treatment facilities application of an irradiation technique was investigated in this study for industrial water reuse. Samples were filtered using a sand filter to remove particles. Co-60 was used as an irradiation source and the irradiation dose was varied from 0.1 kGy to 15 kGy. The major source of colour in secondary treatment effluent was humic substances, which could be easily removed by irradiation with a dose 5 kGy. Bacteria could be also disinfected even at low doses. It was possible to get high quality water for industrial water reuse. But the effluent still contained a small amount of organic compounds. Further treatment, of residual organic compounds will be necessry if the higher quality water is required.