Van Thang Nguyen, Nguyen Phong Thu Huynh, Cong Hao Le
Journal of Environmental Management 271 (2020) 111001
Abstract:
In topsoils, the activity concentrations of natural radionuclides (hereafter NRs) increase due to the addition of NRs from fertilizers, irrigation water, and air dust pollution. On the other hand, various physical-chemical and environmental processes such as radioactive decay, volatilization, leaching, erosion, and plant uptake were responsible for the decrease of the activity concentrations of NRs in the topsoils. In this study, behaviours of 40K, 210Pb, 226Ra, 238U, and 232Th in topsoils were modelled by the CEMC soil model and the HYDRUS-1D model. An exponential equation was proposed for estimating the accumulation rates of these radionuclides in the topsoils. Long-term accumulation of radionuclides was assessed for water spinach (Ipomoea Aquatica Forssk.) soil (here-after VES) and rice (Oryza sativa L.) soil (hereafter RIS). We found that the current agricultural practices caused the increase of 40K activity concentration in the water spinach soil, and 40K, 210Pb, 226Ra, and 232Th activity concentrations in the rice soil. The accumulation rates of radionuclides were in the order 238U <232Th <226Ra <210Pb <40K. 25 years of cultivation with water spinach can increase/decrease +(165 +/- 6) Bq of 40K, – (8.2 +/-0.7) Bq of 210Pb, – (4.3 +/-0.2) Bq of 226Ra, – (7 0.3 +/-0.3) Bq of 238U, and – (1.8 +/-0.1) Bq of 232Th in 1 kg soil. For rice cultivation, these values are +(1004 +/-39), +(3.3 +/-0.2), +(3.0 +/-0.2), – (5.1 +/-0.3), (2.2 +/-0.1) Bq kg-1 for 40K, 210Pb, 226Ra, 238U, and 232Th, respectively.
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A Treatment Planning Comparison between Intensity Modulated Proton Therapy (IMPT) and Volumetric Modulated Arc Therapy (VMAT) for prostate cancer
Thi Cam Thu Nguyen, Thanh Xuan Le
Sci. Tech. Dev. J.; 25(1):2297-2307
Abstract:
Introduction: We made a comparison between IMPT plans and VMAT plans for ten prostate cancer patients with the analysis of dosimetric quantities and EUD for both target volume and OARs.
Methods: Ten patients planned for VMAT were retrospectively replanned with scanned proton beams. Target and OARs were kept as originally delineated in photon plans with the assumption that the change in dose distribution is acceptable. The prescribed dose to the PTV is 74 Gy using an RBE of 1.1. The optimized VMAT plan of each case was normalized using the PTV coverage value obtained from the optimized IMPT plan. For the PTV and OARs, the dosimetric quantities were analyzed. Moreover, EUD with the exponential parameter a with a 95% confidence level was calculated for both the PTV and OARs.
Results: For the PTV, all the averaged dose metrics, including the mean dose, the median dose and the maximum dose, the HI and the EUD, in the IMPT plans were statistically (p0.05) better than those in the VMAT plans. The dose to the PTV from IMPT plans ranged from 69.14.7 to 79.01.1 Gy (RBE), while that from VMAT plans ranged from 68.0 2.8 to 81.6 1.3 Gy (RBE). The mean dose of 2.6 Gy (RBE) to the body from the IMPT plan was significantly (p=0.007) lower than the mean dose of 5.8 Gy (RBE) from the VMAT plans. For all OARs except for the rectum, in the low-to-medium dose region, the volumes receiving low doses in IMPT plans were statistically (p0.05) lower than those in VMAT plans. The IMPT plans show statistically (p0.05) superior dose sparing of the rectum and bladder in comparison to the VMAT plans at the Dmax, Dmean, and V30Gy indices and at all dosimetric indices.
Conclusions: The results show that the IMPT plans were statistically superior to the VMAT plans for both the PTV and OARs. IMPT plans produced a more homogeneous dose in the PTV. For OARs, the volumes receiving the low doses were statistically lower in IMPT plans than in VMAT plans.
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A simple approach for developing model OF Si(Li) detector in Monte Carlo simulation
Huynh Dinh Chuong, Nguyen Thi Truc Linh, Le Thi Ngoc Trang, Vo Hoang Nguyen, Le Hoang Minh , Chau Thanh Tai, Tran Thien Thanh
Huynh Dinh Chuong, Le Thi Ngoc Trang,Vo Hoang Nguyen,Tran Thien Thanh
Applied Radiation and Isotopes, Available online 10 April 2020, 109179
Huynh Dinh Chuong, Le Thi Ngoc Trang, Hoang Duc Tam, Vo Hoang Nguyen, Tran Thien Thanh
NDT & E International Available online 4 May 2020, 102281
A Geant4 procedure for precise simulation of PGNAA prompt gamma‑ray spectrum in a wide energy range up to 8 MeV
Thanh Tai Chau, Ngoc Son Pham, Thien Thanh Tran, Cong Phat Vo, Van Tao Chau
Journal of Radioanalytical and Nuclear Chemistry
Abstract:
In reality, after subtracting the beam background from the prompt g-ray spectrum induced by the irradiated sample with the same time measurement, it still exists the remaining g-ray background induced by the nuclei capturing the thermal neutrons scattered by the sample. This makes it difficult to validate the accuracy of the PGNAA detector response between the simulation and the experiment in the wide energy range. In this study, a simple method to construct the remaining g-ray background in the simulation prompt g-ray spectrum of 35Cl(n,g)36Cl reaction is proposed. Then the simulation prompt g-ray spectrum with the remaining g-ray background is compared to the experimental spectrum to validate the simulation PGNAA detector response in the energy range from 0.1 MeV to about 9 MeV.
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