• Title/Summary/Keyword: Monte-Carlo and Calibration

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The Comparative Analysis of External Dose Reconstruction in EPID and Internal Dose Measurement Using Monte Carlo Simulation (몬테 카를로 전산모사를 통한 EPID의 외부적 선량 재구성과 내부 선량 계측과의 비교 및 분석)

  • Jung, Joo-Young;Yoon, Do-Kun;Suh, Tae-Suk
    • Progress in Medical Physics
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    • v.24 no.4
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    • pp.253-258
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    • 2013
  • The purpose of this study is to evaluate and analyze the relationship between the external radiation dose reconstruction which is transmitted from the patient who receives radiation treatment through electronic portal imaging device (EPID) and the internal dose derived from the Monte Carlo simulation. As a comparative analysis of the two cases, it is performed to provide a basic indicator for similar studies. The geometric information of the experiment and that of the radiation source were entered into Monte Carlo n-particle (MCNPX) which is the computer simulation tool and to derive the EPID images, a tally card in MCNPX was used for visualizing and the imaging of the dose information. We set to source to surface distance (SSD) 100 cm for internal measurement and EPID. And the water phantom was set to be 100 cm of the source to surface distance (SSD) for the internal measurement and EPID was set to 90 cm of SSD which is 10 cm below. The internal dose was collected from the water phantom by using mesh tally function in MCNPX, accumulated dose data was acquired by four-portal beam exposures. At the same time, after getting the dose which had been passed through water phantom, dose reconstruction was performed using back-projection method. In order to analyze about two cases, we compared the penetrated dose by calibration of itself with the absorbed one. We also evaluated the reconstructed dose using EPID and partially accumulated (overlapped) dose in water phantom by four-portal beam exposures. The sum dose data of two cases were calculated as each 3.4580 MeV/g (absorbed dose in water) and 3.4354 MeV/g (EPID reconstruction). The result of sum dose match from two cases shows good agreement with 0.6536% dose error.

GEANT4-based Monte Carlo Simulation of Beam Quality Correction Factors for the Leksell Gamma Knife® PerfexionTM

  • Schaarschmidt, Thomas;Kim, Tae Hoon;Kim, Yong Kyun;Yang, Hye Jeong;Chung, Hyun-Tai
    • Journal of the Korean Physical Society
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    • v.73 no.12
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    • pp.1814-1820
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    • 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.

Estimation of the Fundamental Matrix using a Non-linear Minimization Technique and Its Accuracy Analysis (비선형 최소화에 의한 F행렬 추정 및 정확도 분석)

  • Eom, Seong-Hun;Lee, Jong-Su
    • Journal of the Institute of Electronics Engineers of Korea SP
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    • v.38 no.6
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    • pp.657-664
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    • 2001
  • It is possible to extract a 3D models from its multiple views using the self-calibration. Though it is possible to construct 3D models of objects from their multiple views, accuracy of 3D models depends on the fundamental matrix estimated between two views. In this paper, we show the fundamental matrix accuracy can be improved by taking a non-linear minimization technique. Furthermore, the corresponding points which are completely mismatches or have greater discrepancy errors in their locations, reduce the fundamental matrix accuracy. Thus, applying the Monte Carlo technique and the non-linear minimization Levenberg-Marquardt method to remove the outliers, we can estimate the fundamental matrix with the higher accuracy.

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Measuring and unfolding fast neutron spectra using solution-grown trans-stilbene scintillation detector

  • Nguyen Duy Quang;HongJoo Kim;Phan Quoc Vuong;Nguyen Duc Ton;Uk-Won Nam;Won-Kee Park;JongDae Sohn;Young-Jun Choi;SungHwan Kim;SukWon Youn;Sung-Joon Ye
    • Nuclear Engineering and Technology
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    • v.55 no.3
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    • pp.1021-1030
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    • 2023
  • We propose an overall procedure for measuring and unfolding fast neutron spectra using a trans-stilbene scintillation detector. Detector characterization was described, including the information on energy calibration, detector resolution, and nonproportionality response. The digital charge comparison method was used for the investigation of neutron-gamma Pulse Shape Discrimination (PSD). A pair of values of 600 ns pulse width and 24 ns delay time was found as the optimized conditions for PSD. A fitting technique was introduced to increase the trans-stilbene Proton Response Function (PRF) by 28% based on comparison of the simulated and experimental electron-equivalent distributions by the Cf-252 source. The detector response matrix was constructed by Monte-Carlo simulation and the spectrum unfolding was implemented using the iterative Bayesian method. The unfolding of simulated and measured spectra of Cf-252 and AmBe neutron sources indicates reliable, stable and no-bias results. The unfolding technique was also validated by the measured cosmic-ray induced neutron flux. Our approach is promising for fast neutron detection and spectroscopy.

Evaluation of Clinical Risk according to Multi-Leaf Collimator Positioning Error in Spinal Radiosurgery (척추 방사선수술 시 다엽콜리메이터 위치 오차의 임상적 위험성 평가)

  • Dong‑Jin Kang;Geon Oh;Young‑Joo Shin;Jin-Kyu Kang;Jae-Yong Jung;Boram Lee
    • Journal of radiological science and technology
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    • v.46 no.6
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    • pp.527-533
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    • 2023
  • The purpose of this study is to evaluate the clinical risk of spinal radiosurgery by calculating the dose difference due to dose calculation algorithm and multi-leaf collimator positioning error. The images acquired by the CT simulator were recalculated by correcting the multi-leaf collimator position in the dose verification program created using MATLAB and applying stoichiometric calibration and Monte Carlo algorithm. With multi-leaf collimator positioning error, the clinical target volume (CTV) showed a dose difference of up to 13% in the dose delivered to the 95% volume, while the gross tumor volume (GTV) showed a dose difference of 9%. The average dose delivered to the total volume showed dose variation from -8.9% to 9% and -10.1% to 10.2% for GTV and CTV, respectively. The maximum dose delivered to the total volume of the spinal cord showed a dose difference from -14.2% to 19.6%, and the dose delivered to the 0.35 ㎤ volume showed a dose difference from -15.5% to 19.4%. In future research, automating the linkage between treatment planning systems and dose verification programs would be useful for spinal radiosurgery.

Runoff Analysis of Modified TOPMODEL with Subsurface Storm Flow Generation Mechanism (지표하 흐름을 고려한 개선된 TOPMODEL의 유출분석연구)

  • Lee, Hak-Su;Han, Ji-Yeong;Kim, Gyeong-Hyeon;Kim, Sang-Hyeon
    • Journal of Korea Water Resources Association
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    • v.34 no.4
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    • pp.403-411
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    • 2001
  • This paper investigates the applicability of a modified version of TOPMODEL considering shallow subsurface storm flow in a forested mountaneous catchment. The macroporous soil structure provides a hydrological pathway for rapid runoff generation. A modified version of TOPMODEL introduces the two-storage system to analyze the hydrograph recession including rapid subsurface storm flow component. The two-month continuous hydrologic simulations of sulmachun watershed suggest that a modified version of TOPMODEL represents comprehensive and realistic flow generation mechanism comparing to those of an original version of TOPMODEL. The results of parameter calibration with Monte-Carlo method indicate a modified version of TOPMODEL produces a set of physically meaningful parameters.

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Assessment of Applicability of Portable HPGe Detector with In Situ Object Counting System based on Performance Evaluation of Thyroid Radiobioassays

  • Park, MinSeok;Kwon, Tae-Eun;Pak, Min Jung;Park, Se-Young;Ha, Wi-Ho;Jin, Young-Woo
    • Journal of Radiation Protection and Research
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    • v.42 no.2
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    • pp.83-90
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    • 2017
  • Background: Different cases exist in the measurement of thyroid radiobioassays owing to the individual characteristics of the subjects, especially the potential variation in the counting efficiency. An In situ Object Counting System (ISOCS) was developed to perform an efficiency calibration based on the Monte Carlo calculation, as an alternative to conventional calibration methods. The purpose of this study is to evaluate the applicability of ISOCS to thyroid radiobioassays by comparison with a conventional thyroid monitoring system. Materials and Methods: The efficiency calibration of a portable high-purity germanium (HPGe) detector was performed using ISOCS software. In contrast, the conventional efficiency calibration, which needed a radioactive material, was applied to a scintillator-based thyroid monitor. Four radioiodine samples that contained $^{125}I$ and $^{131}I$ in both aqueous solution and gel forms were measured to evaluate radioactivity in the thyroid. ANSI/HPS N13.30 performance criteria, which included the relative bias, relative precision, and root-mean-squared error, were applied to evaluate the performance of the measurement system. Results and Discussion: The portable HPGe detector could measure both radioiodines with ISOCS but the thyroid monitor could not measure $^{125}I$ because of the limited energy resolution of the NaI(Tl) scintillator. The $^{131}I$ results from both detectors agreed to within 5% with the certified results. Moreover, the $^{125}I$ results from the portable HPGe detector agreed to within 10% with the certified results. All measurement results complied with the ANSI/HPS N13.30 performance criteria. Conclusion: The results of the intercomparison program indicated the feasibility of applying ISOCS software to direct thyroid radiobioassays. The portable HPGe detector with ISOCS software can provide the convenience of efficiency calibration and higher energy resolution for identifying photopeaks, compared with a conventional thyroid monitor with a NaI(Tl) scintillator. The application of ISOCS software in a radiation emergency can improve the response in terms of internal contamination monitoring.

LET Calibration of Fe 500 MeV/u Ions using SSNTD (고체비적검출기를 이용한 500 MeV/u 철 이온의 선에너지전이 교정)

  • KIM, Sunghwan
    • Journal of Sensor Science and Technology
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    • v.25 no.1
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    • pp.41-45
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    • 2016
  • In this study, LET (Linear Energy Transfer) calibration of CR-39 SSNTD (Solid State Nuclear Track Detector) was performed using 500 MeV/u Fe heavy ions in HIMAC (Heavy Ion Medical Accelerator) for high LET radiation dosimetry. The irradiated CR-39 SSNDT were etched according JAXA (Japan Aerospace Exploration Agency) etching conditions. And the etched SSNTD were analyzed by using Image J. Determined dose-mean lineal energy ($\overline{y_D}$) of 500 MeV/u Fe is about 283.3 keV/um by using the CR-39 SSNTD. This value is very similar result compare to the results calculated by GEANT4 Monte Carlo simulation and measured with TEPC active radiation detector. We confirmed that the CR-39 SSNTD was useful for high LET radiation dosimetry such as heavy iron ions.

Choice of Statistical Calibration Procedures When the Standard Measurement is Also Subject to Error

  • Lee, Seung-Hoon;Yum, Bong-Jin
    • Journal of the Korean Statistical Society
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    • v.14 no.2
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    • pp.63-75
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    • 1985
  • This paper considers a statistical calibration problem in which the standard as wel as the nonstandard measurement is subject to error. Since the classicla approach cannot handle this situation properly, a functional relationship model with additional feature of prediction is proposed. For the analysis of the problem four different approaches-two estimation techniques (ordinary and grouping least squares) combined with two prediction methods (classical and inverse prediction)-are considered. By Monte Carlo simulation the perromance of each approach is assessed in term of the probability of concentration. The simulation results indicate that the ordinary least squares with inverse prediction is generally preferred in interpolation while the grouping least squares with classical prediction turns out to be better in extrapolation.

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Comparison of ISO-GUM and Monte Carlo Method for Evaluation of Measurement Uncertainty (몬테카를로 방법과 ISO-GUM 방법의 불확도 평가 결과 비교)

  • Ha, Young-Cheol;Her, Jae-Young;Lee, Seung-Jun;Lee, Kang-Jin
    • Transactions of the Korean Society of Mechanical Engineers B
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    • v.38 no.7
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    • pp.647-656
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    • 2014
  • To supplement the ISO-GUM method for the evaluation of measurement uncertainty, a simulation program using the Monte Carlo method (MCM) was developed, and the MCM and GUM methods were compared. The results are as follows: (1) Even under a non-normal probability distribution of the measurand, MCM provides an accurate coverage interval; (2) Even if a probability distribution that emerged from combining a few non-normal distributions looks as normal, there are cases in which the actual distribution is not normal and the non-normality can be determined by the probability distribution of the combined variance; and (3) If type-A standard uncertainties are involved in the evaluation of measurement uncertainty, GUM generally offers an under-valued coverage interval. However, this problem can be solved by the Bayesian evaluation of type-A standard uncertainty. In this case, the effective degree of freedom for the combined variance is not required in the evaluation of expanded uncertainty, and the appropriate coverage factor for 95% level of confidence was determined to be 1.96.