• Nuclear Engineering and Technology
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• 제52권8호
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• pp.1792-1797
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• 2020

The shielding characteristics of two concrete blocks, widely used in the building industry in Mexico have been determined. These characteristics include the mass interaction coefficients, the linear attenuation coefficients and the half-value layers. The energy-dispersed X-ray fluorescence shows that the percentage mass content of each atom in the sample, and the atomic volume of the constituent elements of a material, plays an important role in its shielding capabilities. The total linear attenuation coefficients and the half-value layers were analyzed for a set of photon energies related to X-rays for diagnosis and cancer treatment with linear accelerators. Our results show that the concrete blocks have similar photon attenuation coefficients than the Portland concrete and better features than gypsum.

• Nuclear Engineering and Technology
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• 제55권6호
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• pp.2166-2171
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• 2023

In the present study, six silicone rubber doped by tellurium borate oxides were fabricated using the casting method. The densities of the fabricated silicon rubber-doped by tellurium borate oxides samples were measured using the Archimedes Method. Moreover, the linear attenuation coefficient of silicone rubber doped tellurium borate oxides samples was evaluated experimentally using the hyper pure germanium, and the recorded linear attenuation coefficient values were affirmed using the theoretical Phy-X program. The experimental measurements were performed using the narrow beam transmission method with radioactive isotopes Am-241, Cs-137, and Co-60 with energies of 59, 661, 1173, and 1332 keV. The linear attenuation coefficient values showed an enhancement by 4.73 times, 1.20 time, 1.17, time, and 1.17 time, respectively at gamma photon energies of 59, 661, 1173, and 1332 keV, when the TeO₂ concentration increased in the fabricated composites from 0 to 50 wt%. The enhancement of the linear attenuation coefficient values has a positive effect on the transmission rate values where the half-value thickness and transmission rate were decreased accompanied by an increase in the RPE.

• 한국의학물리학회지:의학물리
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• 제32권4호
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• pp.153-158
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• 2021

Purpose: This study evaluated the features of a pressure mapping system for patient motion monitoring in radiation therapy. Methods: The pressure mapping system includes an MS 9802 force sensing resistor (FSR) sensor with 2,304 force sensing nodes using 48 columns and 48 rows, controller, and control PC (personal computer). Radiation beam attenuation caused by pressure mapping sensor and signal perturbation by 6 and 10 mega voltage (MV) photon beam was evaluated. The maximum relative pressure value (mRPV), average relative pressure value (aRPV), the center of pressure (COP), and area of pressure distribution were obtained with/without radiation using the upper body of an anthropomorphic phantom for 30 minutes with 15 MV. Results: It was confirmed that the differences in attenuation induced by the FSR sensor for 6 and 10 MV photon beams were small. The differences in mRPV, aRPV, area of pressure distribution with/without radiation are about 0.6%, 1.2%, and 0.5%, respectively. The COP values with/without radiation were also similar. Conclusions: The characteristics of a pressure mapping system during radiation treatment were evaluated on the basis of attenuation and signal perturbation using radiation. The pressure distribution measured using the FSR sensor with little attenuation and signal perturbation by the MV photon beam would be helpful for patient motion monitoring.

• Journal of Radiation Protection and Research
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• 제42권3호
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• pp.154-157
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• 2017

Background: Shielding properties of compound or mixture is presented in terms of mass attenuation coefficients using Monte Carlo simulation. Mass attenuation coefficients of cement, gypsum and the mixture of gypsum and $PbCO_3$ has been investigated using monte carlo MCNPX. Materials and Methods: The mass attenuation coefficients of cement, gypsum and the mixture of gypsum and $PbCO_3$ were calculated for photon energies 365.5, 661.6, 1,173.2, and 1,332.5 keV energies. Results and Discussion: The simulated values of mass attenuation coefficients were compared avaialable experimental results, theoretical values by XCOM and found good comparability of the results. Conclusion: Standard simulation geometry used in the present investigation would be very useful for various types of sample for shielding and dosimetry applications.

• 한국의학물리학회지:의학물리
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• 제22권1호
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• pp.12-17
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• 2011

본 연구는 노발리스용 치료테이블(couch top)을 투과하는 광자선의 감쇠율(attenuation rate)을 기하학적 모델을 통해 계산하고 보정함으로써, 치료부위에 정확한 선량이 전달되게 하는데 그 목적이 있다. 실험은 치료테이블을 투과하는 광자선의 투과율과 감쇠율을 기하학적인 모델에 의해 예측하고 이를 바탕으로 실험적으로 측정된 것을 비교 및 분석하였다. 그 결과 기하학적 모델에 의해 예측된 값과 실험값이 매우 잘 일치하는 것으로 나타났다. 또 실제 임상적용의 가능여부를 판단하기 위하여, 척추 방사선수술(spine radiosurgery)환자의 치료계획에 모델링화한 감쇠율을 보정한 뒤 측정한 중심점 선량과 그렇지 않은 것을 비교하였더니, 전자가 치료계획된 것과의 오차율이 감소함을 보였다. 본 논문에서는 치료테이블을 투과하는 광자선의 기하학적 모델을 통해 투과율과 감쇠율을 계산하고 이를 실험적으로 증명하였다. 이 방법은 노발리스를 이용한 방사선 수술뿐만 아니라 일반적인 방사선 치료에 있어서도 매우 유용할 것으로 판단된다.

• Nuclear Medicine and Molecular Imaging
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• 제41권1호
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• pp.68-69
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• 2007

A 44-year-old female underwent three-phase bone scintigraphy for an evaluation of right hip joint pain. The blood-flow and blood-pool images show a pelvic blush with a photopenic center (doughnut) prior to bladder filling. On the three hour delayed image, the pelvic uptake disappeared. The scintigraphic findings indicated the possibility of an early pregnancy. However, plain radiography demonstrated an intrauterine device. A uterine doughnut developed as a result of photon attenuation of intrauterine device.

• Nuclear Engineering and Technology
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• 제49권8호
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• pp.1758-1771
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• 2017

In this study, to determine the most effective alloy for shielding against gamma-rays, the gamma-ray shielding parameters of six types of cerrobend alloys have been investigated. Gamma-ray interaction with the cerrobend alloys has been discussed mainly in terms of total mass attenuation coefficient (${\mu}_t$), half value layer (HVL), tenth value layer (TVL), effective atomic number ($Z_{eff}$), and effective electron density ($N_{eff}$). These parameters have been calculated by theoretical approach using the ParShield program in a photon energy range between 0.1 MeV and 100 GeV. The dependence of these parameters on the incident photon energy and chemical composition of the cerrobend alloys has been studied.

• 한국의학물리학회지:의학물리
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• 제27권2호
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• pp.79-85
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• 2016

본 연구는 방사선치료에서 방사선 선량전달의 정확도를 높이기 위해 두 종류의 치료테이블 6D robotic couch (BrainLab, Feldkirchen, Germany)와 Standard exact couch (Varian Exact couch$^{TM}$, Varian Medical Systems, Milpitas, CA, USA)를 이용하여 Rail의 위상(In-Out)에 따른 상대선량을 측정하여, 선량감쇠율을 계산하였다. 치료테이블을 투과하는 조사에너지의 조사각 $0^{\circ}$에서 $360^{\circ}$까지의 상대 선량을 각각 측정하였으며, 조사각이 $0^{\circ}$일 때 측정된 선량을 기준으로 하여 $5^{\circ}$ 간격으로 선량의 변화를 측정하고 선량 감쇠율을 계산하였다. Standard exact couch의 광자선 에너지는 6 MV와 10 MV를 사용하였으며 치료테이블의 Rail 위상(In position, Out position)에 따른 상대 선량을 측정하였다. 6D robotic couch는 6 MV와 15 MV의 광자선 에너지를 사용하였다. Standard exact couch의 광자선의 최대 선량차이는 Rail In position에서 6 MV ($175^{\circ}$), 10 MV ($175^{\circ}$)일 때, 선량차이는 각각 16.53%, 12.42%, Out position에서 6 MV ($225^{\circ}$), 10 MV ($225^{\circ}$)일 때, 선량차이는 각각 15.15%, 9.96%였다. 6D robotic couch에서는 6 MV ($130^{\circ}$)와 15 MV ($130^{\circ}$)일 때, 선량차이는 각각 6.82%, 4.92%였다. 본 연구를 통해, 치료테이블의 종류에 따른 선량 감쇠율은 6D robotic couch가 Standard exact couch보다 6 MV에서 조사각 $180^{\circ}$ 기준 약 1% 더 발생함을 확인하였고, Stnadard exact couch인 경우, Sliding rail의 위상(In position, Out position)에 따라 선량 감쇠가 급격히 변화하는 것을 확인하였다.

• Nuclear Engineering and Technology
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• 제53권11호
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• pp.3808-3815
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• 2021

In this paper, the EPICS2017 photoatomic database was used to evaluate the photon mass attenuation coefficients and buildup factors of soils collected at different depths in the Philippine islands. The extraction and interpolation of the library was accomplished at the recommended linear-linear scales to obtain the incoherent and total cross section and mass attenuation coefficient. The buildup factors were evaluated using the G-P fitting method in ANSI/ANS-6.4.3. An agreement was achieved between XCOM, MCNP5, and EPICS2017 for the calculated mass attenuation coefficient values. The buildup factors were reported at several penetration depths within the standard energy grid. The highest values of both buildup factor classifications were found in the energy range between 100 and 400 keV where incoherent scattering interaction probabilities are predominant, and least at the region of predominant photoionization events. The buildup factors were examined as a function of different soil silica contents. The soil samples with larger silica concentrations were found to have higher buildup factor values and hence lower shielding characteristics, while conversely, those with the least silica contents have increased shielding characteristics brought by the increased proportions of the abundant heavier oxides.

• Nuclear Engineering and Technology
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• 제51권6호
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• pp.1633-1637
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• 2019

While considering the photon attenuation coefficient (${\mu}$) and its related parameters for photons shielding, it is necessary to account for its transmitted and reflected photons energy spectra and dose contribution. Monte Carlo simulation was used to study the efficiency of clay ($1.99g\;cm^{-3}$) as a shielding material below 150 keV photon. Am-241 gamma source and an X-ray of 150 kVp were calculated. The calculated value of ${\mu}$ for Am-241 is higher within 5.61% compared to theoretical value for a single-energy photon. The calculated half-value layer (HVL) is 0.9335 cm, which is lower than that of ordinary concrete for X-ray of 150 kVp. A thickness of 2 cm clay was adequate to attenuate 90% and 85% of the incident photons from Am-241 and X-ray of 150 kVp, respectively. The same thickness of 2 cm could shield the gamma source dose rate of Am-241 (1 MBq) down to $0.0528{\mu}Sv/hr$. For X-ray of 150 kVp, photons below 60 keV were significantly decreased with 2 cm clay and a dose rate reduction by ~80%. The contribution of reflected photons and dose from the clay is negligible for both sources.