몬테칼로 전산모사를 이용한 원뿔대 투과형 타겟 모양의 근접치료용 소형 엑스선 선원에 대한 선량분포 평가

안우상,최원식,신성수,박철수,허영철,서정민,김기홍 한국자기학회 2016 한국자기학회 학술연구발표회 논문개요집 Vol.2016 No.05

Dosimetric Optimization of a Truncated Conical-Shaped Transmission Target for Electronic Brachytherapy X-ray Source: A Monte Carlo Study

안우상,최원식,조병철,곽정원,안승도,김현진,조성오,박성호,신승수 한국물리학회 2017 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.71 No.3

The purpose of this study is to determine the optimal target configurations to improve the uniformity of dose distribution for the electronic brachytherapy source. A truncated conical-shaped transmission type was designed. Monte Carlo simulation technique was used to investigate the target thickness, geometry of electron beam, and target angle of a truncated conical-shaped target for the electronic brachytherapy X-ray source. Dosimetric parameters recommended by TG-43U1 protocol were used to determine the optimal target design of electronic brachytherapy source. The target thicknesses for maximizing the transmitted X-ray intensity were approximately 1.2 to 1.5 μm for 0 and 90. In a range of optimal thickness, transmitted X-ray intensity at 90 was approximately 92% of maximum photon intensity. The effects of electron beam shapes on 2D anisotropy functions were investigated at radial distances of 0.5, 1.0, 2.0, 3.0, and 5.0 cm. Minimum variations for all radiation distances and angular ranges were observed for uniform cylindrical electron beam with a radius of 2.0 mm. Anisotropy functions at 0, F(r, 0), were close to unity and slightly more than unity for non-uniform cylindrical (R = 1.0 - 2.0 mm) electron beam and uniform cylindrical electron beam with a radius of 2.0 mm. The angles of target anode between 45 and 50 show minimum fluctuations in the anisotropy functions and are close to unity for F(r, 0). The optimal target configurations are a truncated conical-shaped target having an angle between 45 and 50. It is concluded that tungsten target having the thickness of 1.2 to 1.5 μm and uniform circular with a radius of 2.0 mm as electron beam produces optimal dosimetric characteristics for electronic brachytherapy X-ray source.

Application of a Pelvic Phantom in Brachytherapy Dosimetry for High-dose-rate (HDR) 192Ir Source Based on Monte Carlo Simulations

안우상,Wonsik Choi,신성수,Jinhong Jung 한국물리학회 2014 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.65 No.4

In this study, we evaluate how the radial dose function is influenced by the source position as wellas the phantom size and shape. A pelvic water phantom similar to the pelvic shape of a human bodywas designed by averaging dimensions obtained from computed tomography (CT) images of patientstreated with brachytherapy for cervical cancer. Furthermore, for the study of the effects of sourceposition on the dose distribution, the position of the source in the water phantom was determinedby using the center of mass of the gross target volume (GTV) in the CT images. To obtain thedosimetric parameter of a high-dose-rate (HDR) 192Ir source, we performed Monte Carlo simulationsby using the Monte Carlo n-particle extended code (MCNPX). The radial dose functions obtainedusing the pelvic water phantom were compared with those of spherical phantom with differentsizes, including the Monte Carlo (MC) results of Williamson and Li. Differences between the radialdose functions from this study and the data in the literature increased with the radial distances. The largest differences appeared for spherical phantom with the smallest size. In contrast to thepublished MC results, the radial dose function of the pelvic water phantom significantly decreasedwith radial distance in the vertical direction because full scattering was not possible. When thesource was located in posterior position 2 cm from the center in the pelvic water phantom, thedifferences between the radial dose functions rapidly decreased with the radial distance in the lowervertical direction. If the International Commission on Radiation Units and Measurements bladderand rectum points are considered, doses to these reference points could be underestimated by upto 1% − 2% at a distance of 3 to 6 cm. Our simulation results provide a valid clinical referencedata and can used to improve the accuracy of the doses delivered during brachytherapy applied topatients with cervical cancer.

세기조절방사선치료(IMRT)의 Commissioning 및 정도관리: AAPM TG119 적용

안우상,조병철,Ahn, Woo-Sang,Cho, Byung-Chul 한국의학물리학회 2011 의학물리 Vol.22 No.2

본 연구에서는 미국의학물리학회(AAPM)에서 제안된 세기조절방사선치료(IMRT)의 commissioning 및 정도관리를 위해 제안된 일련의 시험을 통해 본원의 세기조절방사선치료의 정확도를 평가하고 정도관리 절차를 수립하고자 하였다. TG119에 제시된 5가지 세기조절방사선치료의 표적체적: multi-target, 두경부, 전립선, 및 두 가지의 C-shape (easy&hard)을 대상으로 CT 스캔된 팬텀을 이용하여 치료계획시스템에서 IMRT 치료계획을 수행하였다. 얻어진 치료계획을 dynamic sliding window 전달방식으로 팬텀에 조사하였다. 절대 선량은 표적 및 위험장기 부위에 이온 전리함(CC13, IBA)을 이용하여 측정하고, 2차원 상대 선량분포는 EBT2 필름을 사용하여 측정하였다. 측정된 값들은 해당하는 치료계획시스템 계산값과 비교하여 오차의 평균 및 표준편차를 구하였다. 이를 바탕으로 TG119에 제시된 신뢰구간을 계산하여 제시된 값과 비교하였다. 이온 전리함을 이용한 측정 결과에서 표적 및 위험장기에 대한 계산값과 측정값 사이의 평균오차는 각각 $1.2{\pm}1.1%$과 $1.2{\pm}0.7%$이었고, 95% 신뢰구간은 각각 3.4%와 2.6%으로 TG119에서 제시하고 있는 4.5%와 4.7% 이내에 있었다. 필름을 이용한 측정 결과에서는 허용기준 3%/3 mm를 통과하는 감마인덱스는 평균$ 97.7{\pm}0.8%$로 95% 신뢰구간은 3.9%로 TG119에서 제시하고 있는 7.0% 이내에 있었다. 따라서 TG119에서 제시된 일련의 표준화된 시험을 통해 본원의 세기조절방사선치료의 commissioning 및 정도관리를 평가할 수 있었다. 이온 전리함을 이용한 절대 선량에 대한 action level은 표적과 위험장기에서 각각 ${\pm}4%$와 ${\pm}3%$로, EBT2 필름을 이용한 2차원 상대선량분포는 허용기준 3%/3 mm 기준으로 감마인덱스 1이하를 통과하는 비율이 96%로 정할 수 있었다. 이를 통해 TG119에서 제시된 일련의 표준화된 시험을 통해 각 기관의 IMRT 정확도 평가에 대한 객관적인 지표로 이용될 수 있을 것으로 기대된다. The purpose of this study is to evaluate the accuracy of IMRT in our clinic from based on TG119 procedure and establish action level. Five IMRT test cases were described in TG119: multi-target, head&neck, prostate, and two C-shapes (easy&hard). There were used and delivered to water-equivalent solid phantom for IMRT. Absolute dose for points in target and OAR was measured by using an ion chamber (CC13, IBA). EBT2 film was utilized to compare the measured two-dimensional dose distribution with the calculated one by treatment planning system. All collected data were analyzed using the TG119 specifications to determine the confidence limit. The mean of relative error (%) between measured and calculated value was $1.2{\pm}1.1%$ and $1.2{\pm}0.7%$ for target and OAR, respectively. The resulting confidence limits were 3.4% and 2.6%. In EBT2 film dosimetry, the average percentage of points passing the gamma criteria (3%/3 mm) was $97.7{\pm}0.8%$. Confidence limit values determined by EBT2 film analysis was 3.9%. This study has focused on IMRT commissioning and quality assurance based on TG119 guideline. It is concluded that action level were ${\pm}4%$ and ${\pm}3%$ for target and OAR and 97% for film measurement, respectively. It is expected that TG119-based procedure can be used as reference to evaluate the accuracy of IMRT for each institution.

미소선원 적분법과 몬테칼로 방법을 이용한 AAPM TG-43 선량계산 인자 평가: microSelectron HDR Ir-192 선원에 대한 적용

안우상,장원우,박성호,정상훈,조운갑,김영석,안승도,Ahn, Woo-Sang,Jang, Won-Woo,Park, Sung-Ho,Jung, Sang-Hoon,Cho, Woon-Kap,Kim, Young-Seok,Ahn, Seung-Do 한국의학물리학회 2011 의학물리 Vol.22 No.4

고선량률 근접치료에 사용되는 상업용 선원과 치료계획 시스템들은 AAPM TG 43에서 권고하는 점 및 선 선원에 의해 선량분포를 계산한다. 하지만, 근접치료용 선원에 대한 인체 내의 정확한 선량계산을 위해서 3차원 부피의 선원을 고려하는 MC 기반의 선량계산 방법이 필요하다. 본 연구에서는 microSelectron HDR Ir-192 선원을 작은 부분으로 분할하여 계산하는 미소선원 적분법을 이용하여 기하학적 인수를 계산하였다. 또한, 범용 방사선 수송코드인 MCNPX를 사용하여 30 cm 직경의 구형 물 팬텀 내에서 선원의 선량률을 계산하여 비등방성함수와 반경선량함수를 구하였다. 그 결과를 MC 기반 광자 수송코드인 MCPT를 사용하여 계산한 Williamson의 결과와 비교 및 분석하였다. 미소선원 적분법과 선 선원 근사법에 따른 기하학적 인수는 $r{\geq}0.5cm$에서는 0.2% 이내에서 일치하였고 r=0.1 cm일 때 1.33%의 차이를 보였다. 본 연구에서 계산된 비등방성함수와 반경선량함수가 Williamson의 계산된 결과의 차이는 비등방성함수의 경우 r=0.25 cm에 서 2.33%의 가장 큰 R-RMSE를 보였고 $r{\geq}0.5cm$에서는 1% 미만의 R-RMSE를 보였다. 반경선량함수의 경우는 r=0.1~14.0 cm에서 0.46%의 R-RMSE를 보였다. 미소선원 적분법과 선 선원 근사법으로 계산한 기하학적 인수는 $r{\geq}0.1cm$에서 잘 일치하지만 3차원의 Ir-192 선원을 적용하여 계산한 미소선원 적분법이 실제 기하학적 인수를 잘 반영할 것으로 생각된다. r=0.25 cm에서 비등방성함수를 제외하고는 MCPT와 MCNPX의 몬테칼로 코드를 이용하여 얻어진 비등방성함수와 반경선량함수는 각각의 몬테칼로 코드에 대한 불확실성 이내에서 잘 일치함을 확인하였다. 따라서 MCNPX 전산모사 결과를 통해 TG-43의 선량 계산식에 사용된 인자를 Williamson 등의 결과와 비교 및 검증함으로써, 추후 다른 종류의 선원에 대해서도 Monte Carlo 기반의 연구가 가능할 것으로 기대된다. Currently, the dose distribution calculation used by commercial treatment planning systems (TPSs) for high-dose rate (HDR) brachytherapy is derived from point and line source approximation method recommended by AAPM Task Group 43 (TG-43). However, the study of Monte Carlo (MC) simulation is required in order to assess the accuracy of dose calculation around three-dimensional Ir-192 source. In this study, geometry factor was calculated using segmented sources integration method by dividing microSelectron HDR Ir-192 source into smaller parts. The Monte Carlo code (MCNPX 2.5.0) was used to calculate the dose rate $\dot{D}(r,\theta)$ at a point ($r,\theta$) away from a HDR Ir-192 source in spherical water phantom with 30 cm diameter. Finally, anisotropy function and radial dose function were calculated from obtained results. The obtained geometry factor was compared with that calculated from line source approximation. Similarly, obtained anisotropy function and radial dose function were compared with those derived from MCPT results by Williamson. The geometry factor calculated from segmented sources integration method and line source approximation was within 0.2% for $r{\geq}0.5$ cm and 1.33% for r=0.1 cm, respectively. The relative-root mean square error (R-RMSE) of anisotropy function obtained by this study and Williamson was 2.33% for r=0.25 cm and within 1% for r>0.5 cm, respectively. The R-RMSE of radial dose function was 0.46% at radial distance from 0.1 to 14.0 cm. The geometry factor acquired from segmented sources integration method and line source approximation was in good agreement for $r{\geq}0.1$ cm. However, application of segmented sources integration method seems to be valid, since this method using three-dimensional Ir-192 source provides more realistic geometry factor. The anisotropy function and radial dose function estimated from MCNPX in this study and MCPT by Williamson are in good agreement within uncertainty of Monte Carlo codes except at radial distance of r=0.25 cm. It is expected that Monte Carlo code used in this study could be applied to other sources utilized for brachytherapy.

자기장을 이용한 6 MV 광자선의 선량 상승 영역 변조 기술에 관한 유용성 평가

안우상,곽정원,조병철,신성수,최원식 한국자기학회 2016 한국자기학회 학술연구발표회 논문개요집 Vol.2016 No.11

저 강도 자기장을 이용한 광자선의 선량 상승 영역 변조를 위한 빔 스포일러 적용의 예비연구

안우상,곽정원,신성수,정인혜,최원식 한국자기학회 2018 한국자기학회 학술연구발표회 논문개요집 Vol.2018 No.3

공군조종사의 직무요구와 안전동기의 관계 및 A형 성격의 조절효과에 관한 연구

우상천,안관영 대한안전경영과학회 2015 대한안전경영과학회지 Vol.17 No.1

This paper reviewed the relationship between job demands and safety motivation, and the moderating effect of A-type trait in Korean Air Force. Based on the responses from 722 responses, the results of multiple regression analysis appeared as follow; 1) role overload effects positively and role ambiguity effects negatively on intrinsic safety motivation. 2) role conflict effects negatively on extrinsic safety motivation. 3) role ambiguity effects negatively on intrinsic safety motivation in B-type than in A-type trait.

공군조종사의 직무요구와 안전동기의 관계 및 A형 성격의 조절효과에 관한 연구

우상천,안관영 대한안전경영과학회 2015 대한안전경영과학회지 Vol.17 No.1

This paper reviewed the relationship between job demands and safety motivation, and the moderating effect of A-type trait in Korean Air Force. Based on the responses from 722 responses, the results of multiple regression analysis appeared as follow; 1) role overload effects positively and role ambiguity effects negatively on intrinsic safety motivation. 2) role conflict effects negatively on extrinsic safety motivation. 3) role ambiguity effects negatively on intrinsic safety motivation in B-type than in A-type trait.

공군조종사의 직무소진이 안전행동에 미치는 효과와 안전분위기의 조절효과에 관한 연구

우상천,안관영 대한안전경영과학회 2015 대한안전경영과학회지 Vol.17 No.4

This paper reviewed the effect of job burnout on safety outcomes, and the moderating effect of safety climate in Korean Air Force. The prevalence of burnout in air force pilots has not been determined and reviewed. It is also unknown whether pilots’ burnout may affect their safety outcomes(safety action & compliance). The primary objective of this study was to determine the prevalence of burnout and it’s effect on safety outcomes. For cross-sectional survey, 910 questionnaires were sent to pilots in air force, and 722 questionnaires among them were returned effectively. The questionnaire was divided into 4 parts examining pilots’ demographic factors, job burnout, safety outcomes, and safety climates. To test and review proposed hypotheses, hierarchical multiple regression analysis was used. The results of statistical analysis appeared as follow; 1) EE(emotional exhaustion) and RPA(reduced personal accomplishment) effected negatively on safety action. 2) EE and RPA effected negatively on safety compliance. 3) EE effected more positively on safety action in higher SS(superior support) group than in lower SS group. 4) RPA effected more positively on safety compliance in higher SS(superior support) group than in lower SS group. 5) RPA effected more positively on safety action in higher CW(coworker support) group than in lower CW group.