• 한국의학물리학회지:의학물리
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• 제30권4호
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• pp.120-127
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• 2019

Purpose: This study was designed to evaluate the dosimetric performance of Mobius3D by comparison with an aSi-based electronic portal imaging device (EPID) and Octavius 4D, which are conventionally used for patient-specific prescription dose verification. Methods: The study was conducted using nine patients who were treated by volumetric modulated arc therapy. To evaluate the feasibility of Mobius3D for prescription dose verification, we compared the QA results of Mobius3D to an aSi-based EPID and the Octavius 4D dose verification methods. The first was the comparison of the Mobius3D verification phantom dose, and the second was to gamma index analysis. Results: The percentage differences between the calculated point dose and measurements from a PTW31010 ion chamber were 1.6%±1.3%, 2.0%±0.8%, and 1.2%±1.2%, using collapsed cone convolution, an analytical anisotropic algorithm, and the AcurosXB algorithm respectively. The average difference was found to be 1.6%±0.3%. Additionally, in the case of using the PTW31014 ion chamber, the corresponding results were 2.0%±1.4%, 2.4%±2.1%, and 1.6%±2.5%, showing an average agreement within 2.0%±0.3%. Considering all the criteria, the Mobius3D result showed that the percentage dose difference from the EPID was within 0.46%±0.34% on average, and the percentage dose difference from Octavius 4D was within 3.14%±2.85% on average. Conclusions: We conclude that Mobius3D can be used interchangeably with phantom-based dosimetry systems, which are commonly used as patient-specific prescription dose verification tools, especially under the conditions of 3%/3 mm and 95% pass rate.

• Journal of Magnetics
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• 제21권2호
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• pp.293-297
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• 2016

For mastectomy patients, sufficient doses of radiation should be delivered to the surface of the chest wall to prevent recurrence. A bolus is used to increase the surface dose on the chest wall, whereby the surface dose is confirmed with the use of a virtual bolus during the computerized treatment-planning process. The purpose of this study is an examination of the difference between the dose of the computerized treatment plan and the dose that is measured on the bolus. Part of the left breast of an Anderson Rando phantom was removed, followed by the attainment of computed tomography (CT) images that were used as the basis for computerized treatment plans that were established with no bolus, a 3 mm-thick bolus, a 5 mm-thick bolus, and a 10 mm-thick bolus. For the computerized treatment plan, a prescribed dose regimen was dispensed daily and planning target volume (PTV) coverage was applied according to the RTOG 1304 guidelines. Using each of the established computerized treatment plans, chest-wall doses of 5 points were measured; this chest-wall dose was used as the standard for the analysis of this study, while the level of significance was set at P < 0.05. The measurement of the chest-wall dose with no bolus is 1.6 % to 10.3 % higher, and the differences of the minimum average and the maximum average of the five measurement points are -13.8 and -1.9, respectively (P < 0.05); however, when the bolus was used, the dosage was measured as 3.7 % to 9.2 % lower, and the differences of the minimum average and the maximum average are 7.4 and 9.0, -1.2 and 17.4, and 8.1 and 19.8 for 3 mm, 5 mm, and 10 mm, respectively (P < 0.05). As the thickness of the bolus is increased, the differences of the average surface dose are further increased. There are a variety of factors that affect the surface dose on the chest wall during post-mastectomy radiation therapy, for which verification is required; in particular, a consideration of the appropriate thickness and the number of uses when a bolus is used, and which has the greatest effect on the surface dose on the chest wall, is considered necessary.

• 지질공학
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• 제30권4호
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• pp.577-588
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• 2020

일부 암석의 우라늄 함량이 높은 것으로 알려진 옥천층군 지역의 유효선량을 파악하기 위하여 휴대용 감마선분광분석기를 이용하여 421개 지점에서 지표방사능(40K, eU, eTh)을 측정하였다. 연구지역을 5개의 지질(og1, og2, og3, og4, 화성암)로 구분했을 때 지질별 지표방사능 강도에는 큰 차이가 없었다. 전체 421 암석의 40K, eU, eTh의 함량은 각각 0.7~10.3% (평균 5.2%), 0.6~287.0 ppm (평균 8.5 ppm), 4.0~102.4 ppm (평균 31.3 ppm) 을 보였다. 방사능강도로부터 구한 연구지역의 흡수선량은 28.84~1,714.5 nGy/h의 범위로서(평균 195.4 nGy/h) 지질별 평균값 최저는 og1의 166.3 nGy/h, 최고는 og2의 233.3 nGy/h(중앙값은 198.1 nGy/h였다. 흡수선량으로부터 구한 연구지역의 옥외 유효선량은 0.04~2.10 mSv/y (평균 0.24 mSv/y)의 범위이며 함 우라늄층이 협재된 og2에 위치한 4개 지점을 제외하면 옥외 유효선량이 1 mSv/y를 넘는 지점은 없었다.

• Journal of Radiation Protection and Research
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• 제45권2호
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• pp.81-87
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• 2020

Background: Kori unit #1 is permanently shut down after a 40-year lifetime. The Nuclear Safety and Security Commission recommends establishing initial decommissioning plans for all nuclear and radwaste treatment facilities. Therefore, the Korea Atomic Energy Research Institute (KAERI) must establish an initial and final decommissioning plan for radwaste-treatment facilities. Radiation safety assessment, which constitutes one chapter of the decommissioning plan, is important for establishing a decommissioning schedule, a strategy, and cost. It is also a critical issue for the government and public to understand. Materials and Methods: This study provides a method for assessing external radiation dose to workers during decommissioning. An external dose is calculated following each exposure scenario, decommissioning strategy, and working schedule. In this study, exposure dose is evaluated using the deterministic method. Physical characterization of the facility is obtained by both direct measurement and analysis of the drawings, and radiological characterization is analyzed using the annual report of KAERI, which measures the ambient dose every month. Results and Discussion: External doses are calculated at each stage of a decommissioning strategy and found to increase with each successive stage. The maximum external dose was evaluated to be 397.06 man-mSv when working in liquid-waste storage. To satisfy the regulations, working period and manpower must be managed. In this study, average and cumulative exposure doses were calculated for three cases, and the average exposure dose was found to be about 17 mSv/yr in all the cases. Conclusion: For the three cases presented, the average exposure dose is well below the annual maximum effective dose restriction imposed by the international and domestic regulations. Working period and manpower greatly affect the cost and entire decommissioning plan; hence, the chosen option must take account of these factors with due consideration of worker safety.

• 대한방사선기술학회지:방사선기술과학
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• 제24권1호
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• pp.61-65
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• 2001

This study was conducted to find out gamma dose rate in Seoul, from January to December in 2000, and the following results were achieved ; 1. The annual gamma dose rate in Seoul was $17.24{\mu}R/hr$ as average. 2. The annual gamma dose rate in subway of Seoul was $14.96{\mu}R/hr$ as average. 3. The highest annual gamma dose rate was Dong-daemon ku. 4. Annual gamma dose rate in Seoul was higher autumn than winter.

• Asian Pacific Journal of Cancer Prevention
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• 제15권11호
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• pp.4727-4732
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• 2014

Background: Breast cancers are becoming more frequently diagnosed at early stages with improved long term outcomes. Late normal tissue complications induced by radiotherapy must be avoided with new breast radiotherapy techniques being developed. The aim of the study was to compare dosimetric parameters of planning target volume (PTV) and organs at risk between conformal (CRT) and intensity-modulated radiation therapy (IMRT) after breast-conserving surgery. Materials and Methods: A total of 20 patients with early stage left breast cancer received adjuvant radiotherapy after conservative surgery, 10 by 3D-CRT and 10 by IMRT, with a dose of 50 Gy in 25 sessions. Plans were compared according to dose-volume histogram analyses in terms of PTV homogeneity and conformity indices as well as organs at risk dose and volume parameters. Results: The HI and CI of PTV showed no difference between 3D-CRT and IMRT, V95 gave 9.8% coverage for 3D-CRT versus 99% for IMRT, V107 volumes were recorded 11% and 1.3%, respectively. Tangential beam IMRT increased volume of ipsilateral lung V5 average of 90%, ipsilateral V20 lung volume was 13%, 19% with IMRT and 3D-CRT respectively. Patients treated with IMRT, heart volume encompassed by 60% isodose (30 Gy) reduced by average 42% (4% versus 7% with 3D-CRT), mean heart dose by average 35% (495cGy versus 1400 cGy with 3D-CRT). In IMRT minimal heart dose average is 356 cGy versus 90cGy in 3D-CRT. Conclusions: IMRT reduces irradiated volumes of heart and ipsilateral lung in high-dose areas but increases irradiated volumes in low-dose areas in breast cancer patients treated on the left side.

• Imaging Science in Dentistry
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• 제40권4호
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• pp.165-169
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• 2010

Purpose : To survey the radiographic examination protocol for lateral cephalometric radiographic examinations and to measure their patient doses in Korea and to compare the dose according to the size of hospital, the type of image receptor system, and the installation duration. Materials and Methods : The radiographic examination protocols (kVp, mA, and exposure time) for lateral cephalometric radiography were surveyed with 61 cephalometric radiographic equipments and their patient dose-area product (DAP) measured with a DAP meter (DIAMENTOR M4-KDK, PTW, Freiburg, Germany) for 51 cephalometric radiographic equipments. The radiographic examination protocols and patient doses were compared according to the size of hospital (university dental hospital, dental hospital, and dental clinic), the type of image receptor system (film-based, DR and CR type) and the installation duration, respectively. SPSS 12.0.1 for Windows (SPSS Inc., Chicago, USA) was used for independent t-test and ANOVA test. Results : The average protocols were 77.0 kVp, 12.7 mA, 6.2 second for cephalometric radiography. The average patient dose (DAP) was $128.0mGy\;cm^2$ and 3rd quartile dose (DAP) $161.1mGy\;cm^2$ for cephalometric radiography for adult male. There was no statistically significant difference at average patient DAP according to the size of hospital, the type of image receptor system, and the installation duration, repectively. Conclusion : The average patient dose was $128.0mGy\;cm^2$ and the third quartile patient dose $161.1mGy\;cm^2$ for lateral cephalometric radiography for adult male in Korea.

• Journal of Radiation Protection and Research
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• 제42권4호
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• pp.222-228
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• 2017

Background: On June 18, 2017, Korea's first commercial nuclear reactor, the Kori Nuclear Power Plant No. 1, was permanently suspended, and the capacity of nuclear power generation facilities will be adjusted according to the governments denuclearization policy. In these circumstances, it is necessary to assess the quality of radiation safety management in nuclear power plants in Korea by evaluating the radiation dose associated with them. Materials and Methods: The average annual radiation dose per unit, the annual radiation dose per person, and the annual dose distribution were analyzed using the radiation dose database of nuclear reactors for the last 5 years. The results of our analysis were compared to the specifications of the Nuclear Safety Act and Medical Law in Korea. Results and Discussion: The annual average per unit radiation dose of global major nuclear power generation was 720 man-mSv, while that of Korea's nuclear power plants was 374 manmSv. No workers exceeded 50 mSv per year or 100 mSv in 5 years. The individual radiation dose according to occupational exposure was 0.59 mSv for nuclear workers, 1.77 mSv for non-destructive workers, and 0.8 mSv for diagnostic radiologists. Conclusion: The radiation safety management of nuclear power plants in Korea has achieved the best outcomes worldwide, which is considered to be the result of the as-low-as-reasonably-achievable (ALARA) approach and strict radiation safety management. Moreover, the occupational exposures were also very low.

• Journal of Radiation Protection and Research
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• 제37권4호
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• pp.231-236
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• 2012

This study derived measures to reduce exposure doses by identifying factors which affect the external radiation dose rate of patients treated with radiopharmaceuticals for PET-CT tests. The external radiation dose rates were measured on three parts of head, thorax and abdomen at a distance of 50cm from the surface of 60 PET-CT patients. It showed there are changes in factors affecting the external radiation dose rate over time after the administration of F-18 FDG. The external radiation dose rate was lower in the patients with more water intake than those with less water intake before the injection of radiopharmaceuticals at all three points: right after the injection of radiopharmaceuticals (average 4.17 mins), after the pre-PEET-CT urination step (average 77.47 mins), and right after the PET-CT test (average 114.15 mins). The study also found there is a need to increase the amount of water intake before the injection of radiopharmaceuticals in order to maintain a low external radiation dose rate in patients. This strategy is only possible under the assumption that the quality of the video has not changed after conducting this study on the relations between the image and quality. This study also found a need to use radiopharmaceuticals with the minimum amount needed for each patient because F-FDG doses affects the external radiation dose rate at the point right after the injection of radiopharmaceuticals. Urination frequency was the most significant factor to affect the external radiation dose rates at the point right after the PET-CT test and the point after the pre-PET-CT urination step. There is a need to realize the strategy to increase the urination frequency of patients to maintain the external radiation dose rate low (average 77.47 mins) before and after the injection of radiopharmaceuticals. In addition, at this point, there is a need to take advantage of personal strategies because the external radiation dose rate is lower if the fasting time is shorter, the contrast medium is used, and the amount of water intake is increased after the administration of radiopharmaceuticals. Finally this study found the need to be able to generalize these findings through an in-depth research on the factors affecting the external radiation dose rate, which includes radiopharmaceutical dose, urination frequency, the amount of water intake, fasting time and the use of contrast medium.

• 대한방사선치료학회지
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• 제26권1호
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• pp.59-67
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• 2014

목 적 : 폐암의 정위적체부방사선치료시 실제 적용하고 있는 최대강도투사(MIP) 영상과 호흡위상별(0~90%)영상에서 3차원적으로 재구성된 선량 분포 차이를 평가하고자 한다. 대상 및 방법 : 본원에서 정위적체부방사선치료를 시행한 비소세포성 폐암(NSCLC) 환자 5명을 대상으로 4차원 전산화단층영상을 시행하여 10개의 호흡위상별 영상을 획득한 후 최대강도투사 영상을 재구성하여 각 호흡위상별 치료계획을 수립하였고, 2차원 이온전리함과 선량분석프로그램 COMPASS(IBA dosimetry, Schwarzenbruck, Germany)을 이용하여 3차원적으로 재구성된 선량분포를 측정하였다. 이를 이용하여 치료계획 선량분포와 실제 측정 선량분포의 일치성 여부 및 최대강도투사 영상과 호흡위상별 영상에서 선량 분포의 차이를 정량적으로 비교 분석하였다. 결 과 : 최대강도투사 영상 및 호흡위상별 영상에서의 선량분포의 일치성을 알아보기 위한 감마분석 통과율은 대상 환자 모두 99%이상으로 평가기준을 만족 시켰으며, 각각의 환자들에 대한 최대강도투사 영상과 호흡위상별 영상에서 재구성된 선량의 HI(Homogeneity Index) 차이의 평균은 -0.03~0.04로 크지 않았으며, PTV(Planning Target Volume)의 Dmax 차이는 평균 3.30 cGy, 척수는 평균 40 cGy, 양측 폐, 우폐, 좌폐의 $V_{20}$, $V_{10}$, $V_5$ 차이는 평균 -0.04~2.32% 차이를 나타내었다. 또한 모든 환자에 대한 최대강도투사 영상과 호흡위상별 영상에서 재구성된 선량의 HI 차이의 평균은 -0.03~0.03로 크지 않았으며, PTV의 Dmax 차이의 평균은 10% 영상에서 가장 차이가 작았고, 70% 영상에서 가장 큰 차이를 나타내었다. 척수의 Dmax차이의 평균은 50% 영상에서 가장 차이가 작았고, 0% 영상에서 가장 큰 차이를 나타내었다. 폐 $V_{20}$, $V_{10}$, $V_5$의 차이의 평균은 호흡위상별로 일정한 경향성을 나타내지 않았다. 결 론 : 본 연구를 통해 최대강도투사 영상과 각 호흡위상별 영상에서 측정되어 3차원적으로 재구성된 선량분포차이는 일정한 경향을 나타내지는 않았지만 특정 호흡위상에서 선량 분포 차이가 상이한 경우를 볼 수 있었다. 종양의 위치 및 호흡 움직임이 유사한 대상환자군을 선정하여 체계적인 연구를 통해 데이터화 하게 되면 폐와 같이 움직임이 큰 장기의 정위적체부방사선치료시 특정 호흡위상에서 획득한 영상에서의 치료계획이 실제 치료에 적용되어야 하는지에 대한 적합성 여부를 판단 할 수 있을 것이라고 사료된다.