X-ray photons attenuation characteristics for two tellurite based glass systems at dental diagnostic energies

X-ray photons attenuation characteristics for the two tellarite based glasses Bi2O3\u2013 B2O3\u2013 TeO2\u2013 TiO2 and PbO\u2013ZnO\u2013TeO2\u2013B2O3 have been investigated at dental diagnostic energies (between 30-80 keV) using Geant4 code and WinXcom software. The correlation coefficient (R2) is utilized to evaluate the extent to which Geant4 results are related to the WinXcom data. For the both series, R2 is close to 1 for all samples and this implies a perfect degree of association between the Geant4 and WinXcom data. The linear attenuation coefficient is proportionally increased with addition of TeO2 in both series, which implies that there is a decreasing tendency in the X-ray photon transmission corresponding with an increase in the TeO2 content in the glasses. The half value layer (HVL) decreases as the density increases and this decreasing is very notable at 70 and 80 keV. The maximum HVL for all samples occurs at 80 keV and this implies that the HVL gradually increases as the energy of the X-ray photons increase. Also, the increment of TO2 in the glasses (in both systems) leads to reduce the mean free path and BiTeTi6 and PbTeB6 samples have the lowest MFP. The MFP for both systems was compared with three heavy concretes and the comparison revealed that the selected systems can be utilized to fabricate protection masks used during diagnostic radiation of the head or oral cavity

Shielding features of concrete types containing sepiolite mineral: comprehensive study on experimental, XCOM and MCNPX results

Natural sepiolite mineral is a naturally occurring clay form belonging to a part of layered silicate. Because of its advantages such as low production cost, light-weight and convenient, it may be selected as an alternative shielding material to others. Radiation shielding performances of some concretes to sepiolite and B4C addictive have been researched reported in a wide energy region of 0.08–1.333 MeV using experimental data, MCNP and XCOM. The simulated data obtained by MCNPX are discussed and compared with the experimental results as well as with the XCOM results. The simulations match the experiments very well except for S3 sample. From the measurement, the maximum gamma-ray attenuation was detected in the concrete specimen with 10% sepiolite (S1) while the minimum attenuation of gamma-ray was noted in the concrete specimen with 30% sepiolite (S3). The addition of sepiolite mineral to concretes may be an alternative option that can be used in several radiation protection applications

Evaluation of radiation shielding parameters for optical materials

In this work, we have evaluated the mass attenuation coefficient (μ/ρ), half value layer (HVL) and exposure buildup factors (EBF) for Bi-doped tellurite glass, and Dy-doped borate glass. The results show that the Bi-doped tellurite glass has higher μ/ρ and HVL than Dy-doped borate glass. These results could be useful in the construction of active shielding against hazardous gamma radiation

PHYLLOIDES TUMOUR: REVIEW OF AN UNCOMMON BREAST PATHOLOGY AT A SPECIALIZED CANCER CENTRE

Purpose: Phyllodes tumours are rare breast tumours that comprise almost 1% of breast tumours. The outcome for these tumours is generally considered better than breast cancers. We review the cases of phyllodes tumour presenting to a specialised cancer centre over a 14 year period. Materials and Methods: All case records with the diagnosis of phyllodes tumour between 1999 and 2012 were retrieved from the cancer registry. Patient demographics, tumour site, size, axillary lymph node status, whether primary or recurrent, metastatic status, histological type, type of surgery, any complication, margin positivity, post-operative radiation therapy, local or distant recurrence, morality and follow-up duration were recorded. Data were analysed using SPSS. Results: A total of 77 cases of phyllodes tumour were seen between 1999 and 2012. All patients were female with a mean age of 39.9 years. All patients presented with a breast lump with median duration of 8 months. Almost two-thirds (65%) of the patients presented with primary tumour compared to 10% recurrent tumours and the rest were referred after surgery outside. Median size on histopathology was 5 cm (IQR 3.5–8.5 cm). Over a median follow-up duration of 31 months (IQR 9–48 months), 69 patients (89.6%) were alive, while 3 patients (3.9%) did not survive and 5 patients (6.4%) were lost to follow-up. Recurrence was seen in 10 (13%) patients with median time to recurrence of 12 months (IQR 7–24). Involved axillary lymph nodes and borderline or malignant histopathology were found to be signi cantly associated with recurrence (P = 0.04), while margin positivity, post operative radiation therapy and histopathology were not signi cantly associated with recurrence. Conclusion: Phyllodes tumour is an uncommon breast tumour that is predominantly treated with surgical excision. Although survival with these tumours is better compared to breast cancers, involvement of axillary nodes and borderline or malignant histopathology confer an increased risk of recurrence in these patients. Key words: Breast cancer, phyllodes tumours, survival

A comprehensive study of the energy absorption and exposure buildup factors of different bricks for gamma-rays shielding

The present investigation has been performed on different bricks for the purpose of gamma-ray shielding. The values of the mass attenuation coefficient (µ/ρ), energy absorption buildup factor (EABF) and exposure buildup factor (EBF) were determined and utilized to assess the shielding effectiveness of the bricks under investigation. The mass attenuation coefficients of the selected bricks were calculated theoretically using WinXcom program and compared with MCNPX code. Good agreement between WinXcom and MCNPX results was observed. Furthermore, the EABF and EBF have been discussed as functions of the incident photon energy and penetration depth. It has been found that the EABF and EBF values are very large in the intermediate energy region. The steel slag showed good shielding properties, consequently, this brick is eco-friendly and feasible compared with other types of bricks used for construction. The results in this work should be useful in the construction of effectual shielding against hazardous gamma-rays

X-ray photoelectron spectroscopy (XPS) and radiation shielding parameters investigations for zinc molybdenum borotellurite glasses containing different network modifiers

Zinc molybdenum borotellurite glasses containing different network modifiers with the nominal composition of 60 TeO2–10 B2O3–10 MoO3–10 ZnO–10 MO (MO = Li2O, Na2O, K2O, MgO, CaO, and PbO) were prepared by melt quenching method. The X-ray photoelectron spectroscopy (XPS) studies allow to monitor the structural modifications leading to the formation of bridging oxygens (Te–O–Te, B–O–B, Mo–O–Mo, and Te–O–Mo bonds) and nonbridging oxygens (Te = O, Te–O−M+, Mo–O− bonds in the MoO6 octahedral units, Zn–O bonds from ZnO4) with the addition of alkali (Li, Na, and K), alkaline (Mg, Ca), or heavy metal (Pb) oxides. The Te 3d localized core-levels spectra show an asymmetry due to the existence of different Te-based structural clusters and were fitted with three contributions such as Te ions in TeO4 trigonal bipyramid configuration, Te ions in TeO3 − trigonal pyramid configuration and TeO3+1 polyhedra, respectively. The analysis of the Mo 3d spectra indicates prevailingly Mo6+ ions only. The Zn 2p core-level XPS spectra demonstrate that the zinc is mainly coordinated by four oxygen atoms. The essential radiation shielding parameters were studied for the prepared glasses in the photon energy range 1 keV to 100 GeV using WinXCom software program. Parameters like mass attenuation coefficient (μ/ρ), effective atomic number (Z eff), and mean free path (MFP) are evaluated. Further, by using geometric progression method, exposure buildup factor (EBF) values were also calculated in the incident photon energy range 0.015–15 MeV, up to penetration depth of 40 mfp (mean free path). The macroscopic effective removal cross sections (∑R) for fast neutrons have been calculated. The maximum values of μ/ρ and Z eff were found for PbO-introduced glass though it possesses a lower value for MFP and EBF. The obtained results indicate that PbO-based glass is the best radiation shielding material among the studied glasses

Effect of bismuth in lead germanate glass system on shielding properties for development of gamma-rays shielding materials

In this study, the shielding properties of bismuth lead germanate (BPG) glass system in composition x(Bi2O3)40-x(PbO)60(GeO2) where x = 0 to 40 mol% have been investigated. The shielding parameters, mass attenuation coefficients(µ/ρ), mean free path (MFP) and half value layer (HVL) values have been computed using WinXCom program and variation of shielding parameters of the BPG glasses are discussed for the effect of photon energy and Bi2O3 addition into the glasses. The replacement of PbO by Bi2O3 causes an increase in mass attenuation coefficient, while the MFP and HVL values were decreased. The investigation would be very useful for shielding applications in nuclear technologies

Gamma ray shielding characteristics and exposure buildup factor for some natural rocks using MCNP-5 code

The mass attenuation coefficient μm for eight rock samples having different chemical composition was simulated using the MCNP 5 code in energy range (0.002MeV≤E≤10MeV). Moreover, the μm for the studied rock samples was computed theoretically using XCOM database. The comparison between simulated and computed data for all selected rock samples showed a good agreement with differences varied between 0.01 and 8%. The highest μm was found for basalt rocks M2 and M1 and the lowest one is reported for limestone rocks Dike. The simulated values of the μm then were used to calculate other important shielding parameters such as the mean free path, effective electron density and effective atomic number. The exposure buildup factor EBF was also computed for the selected rocks with the contribution of G-P fitting parameters and the highest EBF attended by the basalt sample Sill and varied between 1.022 and 744 in the energy range between (0.015≤E≤15MeV) but the lowest EBF achieved by basalt sample M2 and varied between 1.017 and 491 in the same energy range. © 201