Evaluation of MOSFETs for entrance dose dosimetry for 6 and 10 MV photons with a custom made build up cap

Copyright © 2007 ACPSEM. All rights reserved. The dcoument attached has been archived with permission from the publisher.Commercially available MOSFETs, Thomson and Nielsen TN502-RD, were evaluated for suitability as an entrance dose in vivo dosimeter for 6MV and 10MV. Detector response was normally distributed around a mean (skewness=-0.01±0.24, kurtosis=-0.09±0.48) with a mean of 110.6 mV/Gy, with a standard deviation of 2.4% at 0.86 Gy. The standard deviation of readings increased with decreasing dose and increased at a rate greater than inverse square. The linearity coefficient was 0.9999. No significant dependence on angle, field size, dose rate, energy or time was observed. As such, they would be useful for entrance dose in vivo dosimetry. With a custom made build up cap corrections were required for field size, wedge, beam energy and tray factors, showing that build up cap design is an important consideration for entrance dose in vivo dosimetry using MOSFETs.J. P. Morton, M. Bhat, A. Kovendy and T. Williamshttp://www.acpsem.org.au/journal/abstract/abstract_3002.html#abs0

Health risk assessment of methyl mercury from fish consumption in a sample of adult Qatari residents

Fish constitutes an essential source of high-quality protein and is, at the same time, the source of exposure to many hazardous contaminants, namely mercury and methyl mercury (MeHg). This study aims at assessing the risk that MeHg poses to the health of adult Qatari residents through fish consumption. Data on fish consumption were collected using a self-administered online survey composed of three sections that collected information about the fish-eating patterns of the participants. The fish species that were reported to be consumed by ≥ 3% of the respondents were sampled and analyzed for their total mercury (T-Hg) content levels. MeHg concentrations were derived from T-Hg content levels using a scenario-based approach. Disaggregated fish consumption and contamination data were combined using the deterministic approach to estimate MeHg intakes. The average, 75th, and 95th percentiles of the MeHg intake estimates were determined and compared to the tolerable weekly intake (TWI) set by the European Food Safety Agency (EFSA) (1.3 μg·kg−1·w−1). All fish samples contained T-Hg at levels ˂ 0.3–0.5 µg/g with a mean value of 0.077 µg/g. The study population had an average fish consumption of 736.0 g/week. The average estimated weekly intakes of MeHg exceeded TWI for some fish consumers including females of childbearing age and those following a high-protein diet. Our study highlights the need to establish regulatory guidelines and dietary advice based on risk/benefit ratio.The study was supported by the central Food laboratory of the ministry of public health.Scopu

Evidence-Based PET for Abdominal and Pelvic Tumours

Evidence-based data about the usefulness of positron emission tomography (PET) and hybrid imaging methods (PET/CT and PET/MRI) in abdominal and pelvic tumours have been collected and discussed in this chapter. These data were divided in three sections: (1) gastrointestinal tumours, (2) uro-genital tumours, (3) gynaecological tumours. Several pooled data (diagnostic and prognostic data), clinical settings (e.g. staging, restaging, treatment evaluation) and radiotracers as fluorine-18 fluorodeoxyglucose (18F-FDG), radiolabelled choline and prostate-specific membrane antigen (PSMA) were considered

Bearing capacity of foundations resting on a spatially random soil

The paper presents the effect of the spatial variability of the soil properties on the ultimate bearing capacity of a vertically loaded shallow strip footing. The deterministic model used is based on numerical simulations using the Lagrangian explicit finite difference code FLAC3D. The cohesion and the angle of internal friction of the soil are modelled as non normal anisotropic random fields. The methodology used for the discretization of the random fields is based on the spectral representation method proposed by Yamazaki and Shinozuka (1988). The results have shown that the average bearing capacity of a spatially random soil is lower than the deterministic value obtained for a homogeneous soil. A critical case appears when the autocorrelation distances are equal to the footing breadth. The average value of the ultimate footing load is more sensitive to the horizontal autocorrelation distance than the vertical one. Finally, it has been shown that accounting for the spatial variability of the soil properties gives a higher reliability index of the foundation than the one obtained with the assumption of random variables

Effects of gold and silver backings on the dose rate around an 125-I seed

NRC publication: Ye

Bearing Capacity of Spatially Random Rock Masses Obeying Hoek-Brown Failure Criterion

In this paper, a probabilistic analysis is presented to compute the ultimate bearing capacity of a strip footing resting on a spatially varying rock mass. The rock is assumed to follow the generalized Hoek-Brown failure criterion. The uniaxial compressive strength of the intact rock (σc) was considered as a random field and the Geological Strength Index (GSI) was modeled as a random variable. The deterministic model was based on numerical simulations. The uncertainty propagation methodology employed in the analysis makes use of a non-intrusive approach to build up a sparse polynomial chaos expansion for the system response. The probabilistic numerical results were presented in the case of a weightless rock mass. The variability of the ultimate bearing capacity was found to decrease with the decrease in the autocorrelation distance. Sobol indices have shown that for the very large values of the autocorrelation distance, the variability of the ultimate bearing capacity is mainly due to σc; however, in the case of very small values of the autocorrelation distance, GSI is the most weighed variable