• 대한방사선기술학회지:방사선기술과학
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• 제20권1호
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• pp.71-75
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• 1997

This study was Investigation that we will become aware of the scattering dose of duty station and TLD value of the radiation exposure by the radiation technologists based on the university hospital located in Kwang ju. The results are followings ; 1. The air of scattering dose in chest, when the number of objects are large, is 2.0 mR in P-A and 4.6 mR in Lat. at the back of X-ray tube 2. Radiologists, radiation exposure in duty station Is 0.22 mSv to 1.96 mSv in general examination, 0.22 mSv to 1.12 mSv in contrast and special examination, 0.26 mSv to 30.96 mSv in angiography, and 0.22 mSv to 0.40 mSv in C.T 3. The value of workig condition reveals 85.5% in general examination, 6% in contrast and special examination, and 5.8% in C.T. When the annual exposure is over 20 mSv, it must be measured again according to ICRP public 60.

• 반도체디스플레이기술학회지
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• 제8권2호
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• pp.1-10
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• 2009

This study describes the electron beam lithography pattern fabrication using the proximity effect correction. When electron beam exposes into electron beam resist, the beam tends to spread inside the substance (forward scattering). And the electron beam reflected from substrate spreads again (back scattering). These two effects influence to distribution of the energy and give rise to a proximity effect while a small pattern is generated. In this article, an electron energy distribution is modeled using Gaussian shaped beam distribution and those parameters in the model are computed to solidify the model. The proximity effect is analyzed through simulations and appropriate corrections to reducing the proximity effect are suggested. It is found that the proximate effect can be reduced by adopting schemes of dose adjustment, and the optimal dose is determined through simulations. The proposed corrected proximity effect correction is proved by experiments.

• 한국의학물리학회지:의학물리
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• 제15권3호
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• pp.140-148
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• 2004

본 연구에서는 PTRAN 전산코드를 사용하여 양성자에 대한 물 흡수선량의 분포를 계산하였다. 먼저 양성자와 물과의 상호작용에 대하여 정리하고 흡수선량의 계산과정에 대하여 기술하였다. 또한 PTRAN의 수송 알고리즘, 파일구조, 그리고 실행방법을 제시하였다. 본 결과에서는 양성자 에너지 60, 100, 150, 200, 250 WeV에 대하여 양성자에 의한 물 흡수선량의 분포가 쿨롱 상호작용과 핵반응의 합으로 주어지며, 브레그 봉우리의 형태가 에너지손실의 통계적 성질과 다중산란에 의존함을 보였다. 본 연구를 통하여 양성자에 대한 물 흡수선량의 구조 해석에 PTRAN 코드가 유용함을 알 수 있었다.

• 한국방사선학회논문지
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• 제14권4호
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• pp.385-390
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• 2020

외부의 환경적인 요인은 인간 건강에 많은 영향을 준다. 특히 요즘시대에 가장 중요한 맹점은 미세먼지이다. 미세먼지는 인간의 호흡기를 통해 흡입되면 폐 속에 깊이 침투되기 때문에 다양한 건강 문제를 발생시킨다. 우리의 생활주변 환경에서는 자동차와 사람이 통행할 수 있는 터널을 쉽게 볼 수 있다. 이번 연구에서는 서울 및 경기도 내의 보행 가능한 터널 7개를 무작위로 선정하여 터널 내부의 먼지 량과 비산 방사선량을 측정하여 먼지 량과 방사선량의 상관관계를 알아보고자 하였다. 측정방법은 날씨가 좋은날 (미세먼지수준: 0~30 ㎍/㎥)과 보통날 (미세먼지수준: 0~80 ㎍/㎥)을 선택하여 터널내부의 먼지 량과 방사선량을 각각이 측정하였다. 측정 결과는 미세먼지 수준이 적은 날 즉, 날씨가 좋은 날은 보행터널 중심에서 10-20 % 먼지가 증가되었으며 미세먼지의 수준이 보통인 날은 터널 초입보다는 터널 중심에서 20-30 % 의 먼지가 증가되는 결과를 얻었다. 반면에 방사선량의 터널 측정결과는 날씨에 의존하지 않고 터널 초입보다는 터널 중심에서 10-20 % 방사선량이 증가가 되는 것으로 측정되었다. 결론적으로 사람이 오랜 시간터널에 머무를 경우에는 비산 먼지와 비산 방사선에 주의를 기울여야한다. 따라서 빈번하게 일반인이 터널보행 시에 본인의 건강을 위해 PM2.5 이하의 필터 마스크 착용을 권고한다.

• 한국의학물리학회지:의학물리
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• 제31권3호
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• pp.54-62
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• 2020

Dose calculation algorithms play an important role in radiation therapy and are even the basis for optimizing treatment plans, an important feature in the development of complex treatment technologies such as intensity-modulated radiation therapy. We reviewed the past and current status of dose calculation algorithms used in the treatment planning system for radiation therapy. The radiation-calculating dose calculation algorithm can be broadly classified into three main groups based on the mechanisms used: (1) factor-based, (2) model-based, and (3) principle-based. Factor-based algorithms are a type of empirical dose calculation that interpolates or extrapolates the dose in some basic measurements. Model-based algorithms, represented by the pencil beam convolution, analytical anisotropic, and collapse cone convolution algorithms, use a simplified physical process by using a convolution equation that convolutes the primary photon energy fluence with a kernel. Model-based algorithms allowing side scattering when beams are transmitted to the heterogeneous media provide more precise dose calculation results than correction-based algorithms. Principle-based algorithms, represented by Monte Carlo dose calculations, simulate all real physical processes involving beam particles during transportation; therefore, dose calculations are accurate but time consuming. For approximately 70 years, through the development of dose calculation algorithms and computing technology, the accuracy of dose calculation seems close to our clinical needs. Next-generation dose calculation algorithms are expected to include biologically equivalent doses or biologically effective doses, and doctors expect to be able to use them to improve the quality of treatment in the near future.

• 한국콘텐츠학회논문지
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• 제14권2호
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• pp.457-466
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• 2014

고 에너지 전자선 치료에 있어서 차폐물질은 종양조직 외 정상조직이나 주요장기를 보호하기 위해 사용된다. 하지만 이러한 물질에서 발생되어지는 산란선은 심부선량에 영향을 줄 수 있으며, 물질원자번호에 따라 다르게 나타난다. 이에 차폐물질로써 사용가능한 알루미늄, 구리, 납 등의 다양한 원자번호 물질을 전하 감약율 95% 되는 두께로 하여 측정과 MCNPX 모의계산으로 산란율을 비교분석하였다. 산란선 영향을 많이 받는 표면의 선량변화율은 최대 물질두께에서 +0.88%, 원자번호에서 +0.43%의 영향을 받으며, 전하 감약율 95% 되는 두께의 알루미늄, 구리, 납 물질은 측정에서 +19.70%, +15.20%, +12.40% 계산에서 +25.00%, +15.10%, +13.70%를 보였다. 이로 인해 산란율은 물질두께가 원자번호보다 많은 영향을 주며, 산란전자가 광자보다 많은 기여를 하고 있음을 알 수 있었다. 이에 임상에서의 적절한 차폐물질은 두께영향 산란선이 적게 방출되는 고 원자번호물질이 적당하다고 사료된다.

• 대한방사선기술학회지:방사선기술과학
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• 제42권6호
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• pp.477-482
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• 2019

Recently, due to the increased use of medical radiation, the radiation exposure of radiation workers should be considered as well as medical exposure of patients. And it is recommended to close the door during radiography. however, In this study, when the door was inevitably opened for radiography, the proposed method was to install the shield as a method of reducing the exposure dose. And its efficiency was analyzed. In simple chest radiography, the measurement point was changed according to the measurement location. Dose rate were measured 10 times for each condition using a dosimeter. And the average value was derived. Using this, the change of dose according to the opening and closing of the door and the installation of the shield was analyzed. Using this, we compared and analyzed the dose change according to the door opening and closing and the installation of the shield, and significance was verified through the SPSS ver. 24. Depending on whether the door was opened or closed, 11,215.35%, 159.0%, 101.9% increased in front of the door in the consol room, behind the wall and behind the lead glass. Depending on the installing of the shield, the 49.2%, 29.6%, 19.9%, 30.6% decrease in front of the door in the examination and consol room, behind the wall and lead glass. In addition, statistical analysis was showed that there were significant differences in both the results according to whether the door was opened or closed and shielding(p<.05). Close the door during radiography. However, when the door should be opened, it was confirmed that the dose rate were reduced by installing the shield. Therefore, to optimize radiation protection, it is recommended to install shields when opening the door.

• 대한기계학회논문집B
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• 제27권8호
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• pp.1191-1199
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• 2003

This paper describes to observe the combustion process of only one droplet cluster. In this study, liquid fuel was atomized by ultrasonic wave to form an acoustically levitated droplet cluster. In order to elucidate the detailed structure of burning process of the droplet cluster, laser tomography method was applied. Time-series planar images of fuel droplets were processed and diameter of the each droplet was calculated based on the Mie-scattering theory. Using these data, the modified droplet group combustion number was estimated in time-series. As the result, when the internal droplet group combustion occur, the modified group combustion number dose not decrease monotonically, but show a tow-staged decreasing process. In all case of combustion process, combustion reactions were measured two types that combustion speed was fast and slow. It was casued by difference of concentration degree and droplet size distribution.

• Transactions on Electrical and Electronic Materials
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• 제3권3호
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• pp.1-7
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• 2002

The developed patterns by direct writing of electron beam are measured by AFM, FESEM and optical profiler of WYKO NT3300. From different measurement methods, the measured linewidths of the patterns are shown a little bit wider than designed pattern size due to electrons scattering effect during direct writing of electron beam. The optimized conditions of these experiments are suggested and explained for the forming of structures below 0.1 ㎛ dimension size. Because of electron scattering effects from the different under layers such as Si, Si$_3$N$_4$ and aluminum, the developed pattern size is also influenced by the accelerated energy of electrons, dose, resist and soft and hard bake conditions in PMMA. The distributions of electron beam and calculations of backscattering coefficient are demonstrated by Monte Carlo simulation. From the measured results, the developed linewidth of PMMA/Al /silicon is shown a little bit wider than that of PMMA/Si$_3$N$_4$/silicon structure due to the backscattering effects.

• Journal of Radiation Protection and Research
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• 제44권4호
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• pp.156-160
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• 2019

Background: To compare the dose of radiation received by the fetus in a pregnant patient irradiated for head and neck cancer using helical tomotherapy and three-dimensional conformal radiation therapy (3DCRT). Materials and Methods: The patient was modeled with a humanoid phantom to mimic a gestation of 26 weeks. Radiotherapy with a total dose of 2 Gy was delivered with both tomotherapy (2.5 and 5.0 cm jaw size) and 3DCRT. The position of the fetus was predicted to be 45 cm from the field edge at the time of treatment. The delivered dose was measured according to the distance from the field edge and the fetus. Results and Discussion: The accumulated dose to the fetus was 1.6 cGy by 3DCRT and 2 and 2.3 cGy by the 2.5 and 5 cm jaw tomotherapy plans. For tomotherapy, the fetal dose with the 2.5 cm jaw was lower than that with the 5 cm jaw, although the radiation leakage was greater for 2.5 cm jaw plan due to the 1.5 fold longer beam-on time. At the uterine fundus, tomotherapy with a 5 cm jaw delivered the highest dose of 2.4 cGy. When the fetus moves up to 35 cm at the 29th week of gestation, the resultant fetal doses for 3DCRT and tomotherapy with 2.5 and 5 cm jaws were estimated as 2.1, 2.7, and 3.9 cGy, respectively. Conclusion: For tomotherapy, scattering radiation was more important due to the high monitor unit values. Therefore, selecting a smaller jaw size for tomotherapy may reduce the fetal dose. however, evaluation of risk should be individually performed for each patient.