BẢN TIN KHOA HỌC

Sensitivity of secondary particle emission to hadronic physics models in GATE/Geant4 proton therapy simulations at 100 MeV

Pham Thi Cam Lai, Nguyen Tri Toan Phuc, Vo Hong Hai

Science & Technology Development Journal 2023, 26(3):2930-2936

Abstract:

Introduction: Proton therapy simulations rely on Monte Carlo techniques, such as the GATE code based on the Geant4 toolkit, to predict dose distribution and secondary particle production. The accuracy of these simulations is heavily influenced by the chosen physics models.

Methods: In this study, we analyzed three Geant4 hadronic physics models, BIC, BERT, and INCL++, by calculating the angular and energy distributions of secondary neutrons and gamma particles. We conducted GATE/Geant4 simulations on a water phantom irradiated with a 100 MeV proton beam.

Results: Our investigation revealed notable differences in the angular and energy distributions of emitted particles among the three models.

Conclusion: This study emphasizes the necessity of carefully selecting a hadronic physics model for GATE/Geant4 simulations in proton therapy.

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Ba Ngoc Vu, Thien Ngoc Bui, Phong Thu Nguyen Huynh, Hao Cong Le, Phuong Truc Huynh, Hong Loan Thi Truong

Journal of Radioanalytical and Nuclear Chemistry

Abstract:

In this work, the radon exhalation, annual effective dose and excess lifetime cancer risks due to the exposure of radon released from raw building materials containing fly ash of different fractions were evaluated. The ²²⁶Ra and ²²²Rn concentrations were evaluated by the measurements on HPGe gamma spectrometer, RAD 7 radon detector combined with model calculation of radon exhalation for standard rooms. The results indicated that the emanation fraction for fly ash is lower than the corresponding value for soils and rocks. The surveyed building materials of containing fly ash can result in an indoor radon concentration up to 1.7 Bq m⁻³ which is below the recommended value of 100 Bq m⁻³ by WHO, the annual effective dose increases from 0.007 to 0.022 mSv year⁻¹, the excess lifetime cancer risks ranges from 0.027 × 10^–3 to 0.085 × 10^–3 with the ratio of 3.2 for the additional fly ash content in cement up to 75%. In the meanwhile, it has a down trend and influences inconsiderably on these parameters for sand. The obtained mean annual effective doses are lower than the dose limitation of 10 mSv year⁻¹ recommended for occupational workers.

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N. Tomida, T.N.T.Ngan, et al.

Physical Review Letters 124, 202501 (2020)

Abstract:

We measured missing mass spectrum of the 12C(γ,p) reaction for the first time in coincidence with potential decay products from η' bound nuclei. We tagged an (η + p) pair associated with the η'N → ηN process in a nucleus. After applying kinematical selections to reduce backgrounds, no signal events were observedinthebound-stateregion.An upper limit of the signal cross section in the opening angle cosθ^ηp_lab < -0.9 was obtained to be 2.2 nb/sr at the 90% confidence level. It is compared with theoretical cross sections, whose normalization ambiguity is suppressed by measuring a quasifree η' production rate. Our results indicate a small branching fraction of the η'N → ηN process and/or a shallow η'-nucleus potential.

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Author: Thu T.C.Nguyen, Binh T.Nguyen, Nhon V.Mai

Purpose

Under geometrical uncertainties, different plan evaluation methods have been suggested but the dose distribution at a specified confidence level being highly desirable is lacking. In this work, we used the DVPH (Dose Volume Population Histogram) tool to evaluate the dose distribution of CTVs and OARs (Organs at Risk) and validate the PTV concept at a certain confidence level.

Methods

The plans were evaluated using PTV DVH and the DVPH approach. The DVPH approach is based on statistical analyzing of multiple CTV DVHs under geometrical errors with corresponding occurring probabilities. The random and systematic geometrical errors, assumed to follow a Gaussian distribution, are simulated by shifting the CT images.

Results

For target doses, the results showed that the minimum dose to PTV does not represent the minimum dose to the CTV. For two prostate cases, the minimum doses reduced from 98% and 95% of prescribed dose from PTV DVH to 89% and 92% of prescribed dose from CTV 90% CL-DVPH (90% Confidence Level-DVPH). This reduction was also seen in head and neck cases, from 95% to 68% and 74% of prescribed dose. For OAR doses, OAR DVHs underestimated the OAR dose receiving.

Conclusions

With the DVPH tool, the results showed that the minimum dose to the PTV is not a representative of the minimum dose to the CTV in IMPT at the 90% confidence level. The OAR DVH does not match any OAR CL-DVPHs.

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Rapid method for determining elemental composition in oxide powder sample using Rayleigh-COMPTON scattering technique

Le Hoang Minh, Pham Thi Anh Nhung, Huynh Dinh Chuong, Nguyen Thi Truc Linh, Phan Nguyen Hoang Long, Tran Thien Thanh

Radiation Physics and Chemistry, Available online 28 March 2024

Abstract:

This study presents an innovative approach utilizing gamma scattering techniques to precisely determine the composition percentage in a two-component oxide compound. The experiment involved a ²⁴¹Am gamma-ray source emitting 59.54 keV radiation and a Si(Li) detector to capture Rayleigh and Compton scattering signals from oxide powder samples. These samples were meticulously prepared by blending Pb₃O₄ and ZnO, with Pb₃O₄ proportions ranging from 0% to 100%. To ensure accuracy, eleven standard samples were employed to generate standard curves for Rayleigh intensity, Compton intensity, and the Rayleigh-Compton ratio. The key finding of this research was the calculation of composition percentages for the four samples under investigation, derived from experimental data and the standard curve. Validation against reference materials revealed a minimal relative deviation of approximately 1.0% when estimating the Pb₃O₄ ratio, showcasing the precision and potential applicability of this method in material science and analysis.

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Quantization-constrained parameter method for studying 𝛼 and cluster decay

Nguyen Thi Huyen Nga, Le Hoang Chien, Nguyen Tri Toan Phuc, Chau Van Tao

Phys. Rev. C 113, 044608 (2026)

Abstract

We propose a Quantization-Constrained Parameter Method (QCPM) for determining the Woods-Saxon (WS) potential depth 𝑉₀ and diffuseness 𝑎 in studies of 𝛼 and cluster decay half-lives. In this approach, the parameters are derived analytically by imposing the Bohr-Sommerfeld (BS) quantization condition, thereby eliminating the need for parameter fitting. The calculated diffuseness values exhibit a strong dependence on nuclear shell structure. The reliability of the QCPM-derived WS potential is validated through optical model analyses of elastic 𝛼 scattering data. The resulting 𝛼 and cluster decay half-lives show good agreement with experimental values. Our results highlight the significant role of daughter-nucleus deformation in improving the consistency between theoretical predictions and experimental data. In addition, we introduce a modified Woods-Saxon (mWS) potential that effectively approximates the surface behavior of folding potentials incorporating the nuclear medium effect. This modification leads to closer agreement with the measured half-lives. Free of adjustable parameters such as 𝑉₀ and 𝑎, the QCPM enhances the predictive power of phenomenological potentials for 𝛼 and cluster decay studies.

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