• Nuclear Engineering and Technology
• /
• 제53권10호
• /
• pp.3158-3163
• /
• 2021

Chromium material is commonly used for fusion plasma facing applications because of the low neutron activation property. The Monte Carlo method is one of the useful ways to investigate the ion-target interactions. In this study, Chromium target irradiated by protons was investigated using Monte Carlo based simulation tools. In this context, the calculations of radiation damage on Chromium material irradiated with protons at 17.9 and 22.3 MeV energies were carried out using GEANT4 and SRIM codes. Besides, the cross sections for proton interaction with Chromium target were calculated by the TALYS 1.9 code using CTM + FGM, BSFGM, and GSFM level densities. As a result, GEANT4, SRIM and TALYS 1.9 codes provide a suitable tool for the predictions of radiation damage and cross cross section with proton irradiation.

• 대한방사선기술학회지:방사선기술과학
• /
• 제45권5호
• /
• pp.449-455
• /
• 2022

This study is to present a Geant4 code for the simulation of the absorbed dose distribution given by a medical linac for 6 MV photon beam. The dose distribution was verified by comparison with calculated beam data and beam data measured in water phantom. They were performed for percentage depth dose(PDD) and beam profile of cross-plane for two field sizes of 10 × 10 and 15 × 15 cm². Deviations of a percentage and distance were obtained. In energy spectrum, the mean energy was 1.69 MeV. Results were in agreement with PDD and beam profile of the phantom with a tolerance limit. The differences in the central beam axis data 𝜹₁ for PDD had been less than 2% and in the build up region, these differences increased up to 4.40% for 10 cm square field. The maximum differences of 𝜹₂ for beam profile were calculated with a result of 4.35% and 5.32% for 10 cm, 15 cm square fields, respectively. It can be observed that the difference was below 4% in 𝜹₃ and 𝜹₄. For two field sizes of 𝜹_50-90 and RW₅₀, the results agreed to within 2 mm. The results of the t-test showed that no statistically significant differences were found between the data for PDD of 𝜹₁, p>0.05. A significant difference on PDD was observed for field sizes of 10 × 10 cm², p=0.041. No significant differences were found in the beam profile of 𝜹₃, 𝜹₄, RW₅₀, and 𝜹_50-90. Significant differences on beam profile of 𝜹₂ were observed for field sizes of 10 × 10 cm², p=0.025 and for 15 × 15 cm², p=0.037. This work described the development and reproducibility of Geant4 code for verification of dose distribution.

• Journal of the Korean Physical Society
• /
• 제73권12호
• /
• pp.1814-1820
• /
• 2018

With the publication of TRS-483 in late 2017 the IAEA has established an international code of practice for reference dosimetry in small and non-standard fields based on a formalism first suggested by Alfonso et al. in 2008. However, data on beam quality correction factors ($k^{f_{msr},f_{ref}}_{Q_{msr},Q_0}$) for the Leksell Gamma $Knife^{(R)}$ $Perfexion^{TM}$ is scarce and what little data is available was obtained under conditions not necessarily in accordance with the IAEA's recommendations. This study constitutes the first systematic attempt to calculate those correction factors by applying the new code of practice to Monte Carlo simulation using the GEANT4 toolkit. $k^{f_{msr},f_{ref}}_{Q_{msr},Q_0}$ values were determined for three common ionization chamber detectors and five different phantom materials, with results indicating that in most phantom materials, all chambers were well suited for reference dosimetry with the Gamma $Knife^{(R)}$. Similarities and differences between the results of this study and previous ones were also analyzed and it was found that the results obtained herein were generally in good agreement with earlier PENELOPE and EGSnrc studies.

• Nuclear Engineering and Technology
• /
• 제55권7호
• /
• pp.2483-2488
• /
• 2023

Differential die-away analysis (DDAA) technology is a special nuclear material (SNM) active detection analysis technology. Be a nuclear material shielded or not, the technology can reveal the existence of nuclear materials by inducing fission from an external pulsed neutron source. In this paper, a detection model based on DDAA analysis technology was established by geant4 Monte Carlo simulation software, and the optimal sensitivity of the detection system is achieved by optimizing different configurations. After the geant4 simulation and optimization, a prototype was established, and experimental research was carried out. The result shows that the prototype can detect 200 g of ²³⁵U in a steel cylinder shield that's of 1.5 cm in inner diameter, 10 cm in thickness and 280 kg in weight.

• 한국의학물리학회지:의학물리
• /
• 제22권2호
• /
• pp.79-84
• /
• 2011

본 연구에서는 GEANT4 toolkit을 이용하여 의료용 선형가속기에 대한 몬테칼로(Monte Carlo) 전산모사를 하였다. Medical Linac2 예제를 수정해서 사용하였다. 에너지스펙트럼, 최빈에너지, 평균에너지를 EGS4 결과와 비교 하였고 선속의 중심에서부터 반경에 따른 단위면적당 광자수, 단위면적당 에너지, 평균에너지를 분석하였다. 그 결과 EGS4 결과와 큰 차이를 보이지 않기 때문에 Medical Linac2 예제의 선속특성에 관한 전산모사에 큰 문제점은 없는 것으로 판단된다. 같은 헤드구조에서도 Physics List의 모델에 따라서는 결과에 차이가 발생하므로 연구 환경에 알맞은 Physics List 모델을 선택하는 것이 중요하다고 판단된다. 본 연구는 처음 몬테칼로 전산모사를 접하는 사용자가 선속특성에 대한 전산모사를 수행하고 6 MV 광자선속의 특성을 분석하는 과정에 많은 도움이 될 것으로 사료된다.

• 한국방사선학회논문지
• /
• 제13권4호
• /
• pp.637-643
• /
• 2019

인체 내부의 움직임을 확인하기 위해서 CT에서 얻은 DICOM 파일과 Geant4 코드를 이용하여 폐암환자를 모사하였다. 자체 제작한 Moving Phantom에 가상의 종양을 만들어 종양의 움직임이 호기와 흡기에 위치했을 때 종양의 움직임을 측정하는 방법과 이것을 적용하여 Moving Phantom을 통한 치료계획시의 선량분포와 호흡동조 폐암환자 PTV내의 종양의 정확도를 확인하고자 한다. 움직이는 영역이 3cm 이상이라도 40~70 % 구간에서 호흡 동조 방사선치료를 시행 할 경우 97% 이상 효과적임을 확인하였다. 움직이는 표적에 호흡 연동 방사선치료를 적용한 선량 분포인데 이는 구동 팬텀 내 필름으로 측정한 것으로 90%가 포함되는 선량분포의 오차범위 3mm이내에 분포됨을 알 수 있었다. 실제 환자 호흡곡선의 경우 호기 상태의 시간이 사인곡선에 비하여 길기 때문에 치료시간이 이보다 짧을 수 있음을 확인하였다.

• 핵의학기술
• /
• 제18권2호
• /
• pp.57-61
• /
• 2014

국내 갑상선암 환자의 발병률이 증가함에 따라 방사성요오드 치료가 필요한 환자가 증가하고 있다. 방사성 요오드 치료에 이용되고 있는 캡슐용기들 중 1.1 GBq과 5.5 GBq의 국산제품에 설계도면을 바탕으로 차폐체를 구현한 후 366 keV 이상에 감마선들에 대하여 캡슐용기의 방사선 누설선량을 GEANT4 전사모사를 이용하여 평가하였다. 치료용 I-131 캡슐용기 누설선량을 측정하기 위해 각각의 용기에 대하여 용기 표면에서 10 cm 거리 및 100 cm 거리에서의 누설선량을 측정하였다. 용기표면에서 10 cm 거리와 100 cm 거리에서의 누설선량 측정은 방사형으로 발생되는 방사선을 위치별로 측정하기 위해 $10{\times}10{\times}10cm^3$ 부피의 정육면체 형태의 물 팬텀(phantom)을 상부, 상부측면, 측면, 하부측면, 하부 다섯 방향에 설치하여 누설선량을 계산하였다. 용기별로 5개 방향에서 용기표면으로 부터 10 cm, 100 cm 거리에서 전산모사를 수행한 결과 법적 허용기준인 10 cm 거리에서 2.0 mSv/h, 100 cm 거리에서 0.02 mSv/h 이하의 선량 규정과 비교하였을 때 법적기준치보다 현저히 낮은 누설선량이 방출되는 것을 확인하였다.

• 한국의학물리학회지:의학물리
• /
• 제22권2호
• /
• pp.85-91
• /
• 2011

GEANT4 Medical Linac 2 예제 코드를 이용하여 선형가속기 전자선의 에너지 분포를 계산하였다. 입사 전자의 평균 에너지는 6, 9, 12, 16, 20 MeV이었으며, 전자선 특성에 영향을 주는 전자선 산란박 물질, 두께, 위치에 따른 에너지 분포를 계산하였다. 산란박 물질은 납, 구리, 알루미늄, 금을 사용하였다. 산란박 위치를 변경하여 선형 가속기 헤드 속 산란박 위치가 전자 및 광자 에너지 분포에 미치는 영향을 분석하였다. 의료용 선형가속기 시뮬레이션의 기초자료인 에너지 분포에 대해 여러 가지 산란박 조건을 적용하여 경향을 나타내었다. 이 결과는 선형가속기 헤드 설계에 이용될 수 있을 것으로 본다.

• 한국의학물리학회지:의학물리
• /
• 제27권3호
• /
• pp.125-130
• /
• 2016

Dual energy computed tomography (DECT) is used to classify two materials and quantify the mass density of each material in the human body. An energy modulation filter based DECT could acquire two images, which are generated by the low- and high-energy photon spectra, in one scan, with one tube and detector. In the case of DECT using the energy modulation filter, the filter should perform the optimization process for the type of materials and thicknesses for generating two photon spectra. In this study, Geant4 Monte-Carlo simulation toolkit was used to execute the optimization process for determining the property of the energy modulation filter. In the process, various materials used for the energy modulation filter are copper (Cu, $8.96g/cm^3$), niobium (Nb, $8.57g/cm^3$), stannum (Sn, $7.31g/cm^3$), gold (Au, $19.32g/cm^3$), and lead (Pb, $11.34g/cm^3$). The thickness of the modulation filter varied from 0.1 mm to 1.0 mm. To evaluate the overlap region of the low- and high-energy spectrum, Geant4 Monte-Carlo simulation is used. The variation of the photon flux and the mean energy of photon spectrum that passes through the energy modulation filter are evaluated. In the primary photon spectrum of 80 kVp, the optimal modulation filter is a 0.1 mm lead filter that can acquire the same mean energy of 140 kVp photon spectrum. The lead filter of 0.1 mm based dual energy CBCT is required to increase the tube current 4.37 times than the original tube current owing to the 77.1% attenuation in the filter.

• Nuclear Engineering and Technology
• /
• 제53권4호
• /
• pp.1259-1265
• /
• 2021

In the present study, a large-area hybrid gamma imaging system was designed by adopting coded aperture imaging on the basis of a large-area Compton camera to achieve high imaging performance throughout a broad energy range (100-2000 keV). The system consisting of a tungsten coded aperture mask and monolithic NaI(Tl) scintillation detectors was designed through a series of Geant4 Monte Carlo radiation transport simulations, in consideration of both imaging sensitivity and imaging resolution. Then, the performance of the system was predicted by Geant4 Monte Carlo simulations for point sources under various conditions. Our simulation results show that the system provides very high imaging sensitivity (i.e., low values for minimum detectable activity, MDA), thus allowing for imaging of low-activity sources at distances impossible with coded aperture imaging or Compton imaging alone. In addition, the imaging resolution of the system was found to be high (i.e., around 6°) over the broad energy range of 59.5-1330 keV.