Thickness determination of material plates by gamma-ray transmission technique using calibration curves constructed from Monte Carlo simulation
Huynh Dinh Chuong, Le Thi Ngoc Trang, Le Hoang Minh, Nguyen Thi Truc Linh, Hoang DucTam, Tran Thien Thanh
Radiation Physics and Chemistry(2021)
Abstract:
This paper presents a new approach for determining the thickness of material plates by gamma-ray transmission technique using calibration curves obtained from simulated spectra through the Monte Carlo algorithm. The narrow transmitted gamma-ray beam from a collimated source of 137Cs (with the energy of 661.7 keV) for different thicknesses of the metal plates (aluminum, copper, and steel) was recorded by a NaI(Tl) detector. Besides, the Monte Carlo simulations of radiation transport in a model with the same geometry, source, and detector characteristics as in the real experiment were performed to obtain the transmission spectra. A good agreement between the experimental and simulated spectra was observed. The linear calibration curves of the value of ln(R) versus the thickness of material plates were constructed using Monte Carlo simulated data (R is the ratio of the area under a transmitted peak for measurement with sample relative to that for measurement without sample). The unknown thickness of a sample was determined by substituting the experimental value of ln(R) into the linear calibration curve corresponding to such sample. Besides, the range of measurable thickness with the desired accuracy was estimated for each material based on simulated data. The obtained results showed excellent quantitative values even without using any standard plate with known thickness for the calibration.
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The institutional experience of the implementing 4DCT in NSCLC radiotherapy planning
Huy Quang Dang, Cong Thanh Nguyen, Hoat Viet Pham, Linh Duc Tran, Cong Duc Nguyen, Dung Vu Manh Truong, Trang Thi Kieu Hoang, Tao Van Chau
Reports of Practical Oncology and Radiotherapy 2023, Volume 28, Number 4, pages: 445–452
ABSTRACT
Background:The study was to evaluate the effectiveness of dose distribution of four-dimensional computed tomography (4DCT) simulation.
Materials and methods: The gross tumor volume (GTV) and clinical target volume (CTV) were contoured in all 10 respiratory phases of 4DCT in 30 patients with non-small cell lung cancer (NSCLC). Both 3D and 4D treatment plans were made individually for each patient using the planning volume (PTV). The PTV3D was taken from a single CTV plus the recommended margin, and the PTV4D was taken from the 4D internal target volume, including all 10 CTVs plus the setup margins.
Results: The mean PTV was 460 ± 179 (69–820) cm3 for 3DCT and 401 ± 167 (127–854) cm3 for 4DCT (p = 0.0018). The dose distribution (DD) of organs at risk, especially the lungs, was lower for the 4DCT simulation. The V5%, V10%, and V20% of the total lung dose for 4DCT were significantly lower for the 3DCT. However, lung V30% the heart, esophagus, and spinal cord were not significantly different. In addition, the conformity index and the dose heterogeneity index of the PTV were not significantly different. The normal tissue complication probability (NTCP) of the lung and heart was significantly lower for
4DCT than for 3DCT.
Conclusions: The 4DCT simulation gives better results on the NTCP. The organs at risk, especially the lungs, receive a significantly lower DD compared with the 3DCT. The conformity index (CI), heterogeneity index (HI) and the DD to the heart, spinal cord, and esophagus were not significantly different between the two techniques.
Key words: 4DCT simulation technique; 3D-CRT; NTCP; HI; CI
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Huynh Nguyen Phong Thu, Nguyen Van Thang, Le Cong Hao
Journal of Environmental Radioactivity 216 (2020) 106189
The effects of moisture content, grain size, temperature, major elemental composition, and the pH of soils on the radon emanation and diffusion coefficients were evaluated in this study. The emanation and diffusion coefficients are strongly influenced by moisture content and grain size. The radon emanation coefficient increased and the diffusion coefficient decreased with decreasing particle size. However, for soils with large particle sizes, the radon emanation and diffusion coefficient remain almost unchanged with variation in grain size. Comparing five different sized soil particles, the emanation coefficient increased and the diffusion coefficient decreased with moisture content. The radon emanation coefficient reached a constant value with different moisture contents depending on the range of grain sizes. The saturation emanation coefficient for less than 0.1, 0.1–0.2, 0.2–0.3, 0.3–0.5, and more than 0.5 mm sized soil grain ranges are 0.47, 0.42, 0.35, 0.26 and 0.23, respectively, with saturation moisture contents of 16%, 14%, 10%, 6% and 4%, respectively. A drastic increase in radon emanation is found at smaller grain sizes with increasing moisture content. Based on the content of major elements and pH of the soils, the multiple regression indicates that the radon emanation coefficient appears to be significantly dependent on iron content and pH. Effective diffusion coefficient values calculated in our study agree with the results calculated by a previous model. Experimental values show that the temperature dependence of the radon diffusion coefficient follows Arrhenius behavior.
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Systematics of supernumerary nuclear rainbow in inelastic 16O+12C scattering
Nguyen Hoang Phuc, Nguyen Tri Toan Phuc & Do Cong Cuong
Abstract:
We perform a systematic study of inelastic nuclear rainbow scattering for the 16O +12C system to the 2+ (4.44 MeV) state of 12C at incident energies of 100–608 MeV with the coupled-channels method. The recently generalized nearside-farside decomposition for inelastic scattering was applied in combination with the multichannel deflection function analysis to elucidate the origin of the nuclear rainbow phenomenon and the suppression of the primary and supernumerary Airy minima in the inelastic-scattering cross section. The systematic evolution of the Airy minima for the excited 2+ (4.44 MeV) state of 12C was unambiguously determined. Our work suggests that there is no clear shift in the positions of the first Airy minima and a small shift at low energies for the second and third Airy minima between the inelastic- and elastic-scattering cross sections. Using the 𝐾-subamplitudes splitting technique combined with the generalized nearside-farside decomposition and deflection function, the distinct refractive pattern commonly suppressed in the inelastic heavy-ion scattering can be interpreted and provides new insights into the relationship between elastic and inelastic nuclear rainbow scattering.
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Suppression of the nuclear rainbow in the inelasticnucleus–nucleus scattering
Nguyen Hoang Phuc, Dao T. Khoa, Nguyen Tri Toan Phuc, Do Cong Cuong
Eur. Phys. J. A (2021) 57:75
Abstract:
The nuclear rainbow observed in the elasticα-nucleus and light heavy-ion scattering is proven to be due tothe refraction of the scattering wave by a deep, attractive realoptical potential. The nuclear rainbow pattern, established asa broad oscillation of the Airy minima in the elastic cross sec-tion, originates from an interference of the refracted far-sidescattering amplitudes. It is natural to expect a similar rainbowpattern also in the inelastic scattering of a nucleus–nucleussystem that exhibits a pronounced rainbow pattern in theelastic channel. Although some feature of the nuclear rain-bow in the inelastic nucleus–nucleus scattering was observedin experiment, the measured inelastic cross sections exhibitmuch weaker rainbow pattern, where the Airy oscillationis suppressed and smeared out. To investigate this effect, anovel method of the near-far decomposition of the inelasticscattering amplitude is proposed to explicitly reveal the cou-pled partial-wave contributions to the inelastic cross section.Using the new decomposition method, our coupled channelanalysis of the elastic and inelastic12C+12C and16O+12C scattering at the refractive energies shows unambigu-ously that the suppression of the nuclear rainbow pattern inthe inelastic scattering cross section is caused by a destruc-tive interference of the partial waves of different multipoles.However, the inelastic scattering remains strongly refractivein these cases, where the far-side scattering is dominant atmedium and large angles like that observed in the elasticscattering.
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Nguyễn Duy Thông
Tạp chí Khoa học Trường Đại học Cần Thơ, Tập 56, Số chuyên đề: Khoa học tự nhiên (2020)(1):134-140
Tóm tắt:
Tán xạ nhiều lần được xem là nguyên nhân chính dẫn đến các sai số trong việc xác định vị trí của các hạt tới trong thực nghiệm. Hàm phân bố mật độ xác suất của góc tán xạ nhiều lần đóng vai trò quan trọng trong quá trình làm khớp các số liệu thực nghiệm. Hiện nay, nhiều công trình vẫn đang sử dụng hàm phân bố mật độ xác suất của góc tán xạ nhiều lần tuân theo phân bố Gauss. Điều này dẫn đến các sai số trong quá trình làm khớp. Để xác định hàm phân bố mật độ xác suất của góc tán xạ nhiều lần, trong bài báo này, mô phỏng tương tác của hạt tới để đạt được phân bố của góc tán xạ bằng chương trình g4beamline đã được tiến hành và dựa vào các tính toán chi2 và hệ số Kullback-Leibler để xác định số hàm Gauss có thể được áp dụng để miêu tả hàm mật độ xác suất.
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