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The article presents a study which aims to create different female thoracic phantoms with various breast sizes and chest girths. Computational calibration using numerical representations, Mesh and non-uniform rational basis spline (NURBS) geometries were considered in monitoring the lungs of female workers with internal contamination risks. Results showed that the calculation provides typical efficiency correction factors that can be used to optimize the lung monitoring of female workers.

The article describes the process used and adjustments necessary to calculate uranium mass from proportional counting measurements during the field testing phase of the Capstone Depleted Uranium (DU) Aerosol Study. The aerosol samples collected during the study were generated by the perforation of armored combat vehicles and were used to characterize the DU source term for the subsequent Human Health Risk Assessment (HHRA) of Capstone aerosols. For the samples collected during the study, it was determined that the equilibrium between the uranium isotopes and their immediate, beta-emitting progeny has been disrupted when penetrators had perforated target vehicles.

The article discusses a Poisson statistical alternative to the accepted method for calculating detection limits. This method avoids difficulties often encountered with few total counts including excessive false positives and large relative uncertainly in the signal determination. The alternate method includes the uncertainty of the signal counts and defines detection at the same relative uncertainty for all magnitudes of total counts Negative signal results are avoided by the use of the confidence interval method to determine the mode or most probable value which is particularly useful at few total counts.

Standard methods for quantification of airborne bacteria are based on cultivation and counting of grown colonies. From complex natural environments it is known that only a small fraction of the total number of cells can be cultivated on routinely used agar-media. Direct microscopic cell counting after DNA-staining usually generates higher concentrations of one to two magnitudes. The objective of the presented study was to compare the concentrations of airborne bacteria sampled in a composting facility by using for any sample the cultivation on trytic soy agar (TSA) - agar, as well as direct counting after DAPI-staining. The concentrations after counting grown colonies were within a range of 105–107 cfu m-3. Concentrations of direct counted cells ranged between 106–109 microbes m-3. In these comparative measurements only 1.5–15.3% of the airborne bacterial cells enumerated by direct counting formed countable colonies after incubation on TSA-agar. Obviously, cultivation based methods underestimate the real amount of airborne microbes. In addition, from literature it is known that inactive or even dead cells can also have the potential to cause health effects. Consequently, a risk assessment based only on measuring colony forming units may, in some cases, not be sufficient. [ABSTRACT FROM AUTHOR]

This article discusses the Standfast whole body radiation counter as modeled using Monte Carlo simulations. The effect of phantom size, position of the phantom within the counting enclosure on the counting efficiency and photon energy were examined. The manufacturer's recommended positioning, was found to have the most dependence on phantom size the and higher counting efficiencies. The position where the phantom is at the back of the counting enclosure had lower counting efficiencies, and hence higher minimum detectable activities but for emergency response where accuracy is to be preferred over sensitivity, this geometry is better.

The Human Monitoring Laboratory has found an alternate use for a hyperpure gennanium field deployable instrument that was originally designed to be used in a search and identify mode for contraband radioactive material. The instrument, the Ortec Detective, becomes a fully functional spectroscopy system when connected to a laptop computer. In this configuration it can be used as a high-resolution portable whole body counter. This work has determined that the instrument has adequate sensitivity for emergency response with respect to fission and activation products, but not actin ides. The use of Monte Carlo simulations has allowed the HML to calibrate the instrument, partially optimize the counting geometry, and develop a calibration curve that is a function of photon energy and a persons' size. Similarly for thyroid counting, a function has been found that fits counting efficiency to a person's height. The MDA's are a few kilo Becquerels for fission and activation products for a 5-min count in an unshielded environment using a male subject Health Phys. [ABSTRACT FROM AUTHOR]

The W-chair whole body counting geometry, a derivative of the meter-arc counting geometry, has been examined using Monte Carlo simulations to investigate the effect of phantom size on the counting efficiency. Three detector positions were simulated (42 cm, 71 cm, and 100 cm from the chair), with one being very close to the physical counting geometry in use at the Whiteshell Laboratories, to investigate the effects of detector-chair distance. The agreement of the simulations with observed counting efficiencies was within 7% over the energy region of 122 keV to 1,173 keV. The optimum counting geometry was found to be the 71-cm detector-chair distance as this balances both sensitivity and counting efficiency. The range of relative counting efficiencies is 0.94 to 1.13 for all energies studied (126 keV to 2,754 keV) and selected phantom sizes relative to the Reference Man phantom. This range also represents the extent of the activity estimate's uncertainty if no size correction factors are applied during routine counting and shows the W-chair counting geometry to be relatively subject-size independent. [ABSTRACT FROM AUTHOR]

Lung counters are usually calibrated with an anthropometric phantom that has a fixed lung size; however, people have widely varying lung sizes (both volume and dimensions). This work uses a simple Monte Carlo simulation to investigate the effect on the counting efficiency of a lung counter based on a four detector array of 50 mm diameter, 70 mm diameter, or 85 mm diameter as lung size varies. The simulations were carried out at several photon energies (17, 60, 120, and 1,000 keV). Comparing the simulated efficiencies with a reference value close to the lung volume of Reference Man, biases in the range of -21% to 63% were discovered. The values from the Monte Carlo simulation have also been compared with some literature data based on experimental measurements, and the agreement was found to be comparable suggesting that lung volume is indeed a factor that should be considered when trying to make an accurate estimate of a lung burden. [ABSTRACT FROM AUTHOR]

A function has been developed that will fit counting efficiency to chest wall thickness, adipose content of the chest wall, and photon energy. The adipose content of the chest wall is removed as a variable by use of the derived quantity: muscle equivalent chest wall thickness. The function has been tested on experimental data sets obtained from the LLNL and JAERI torso phantoms using a variety of germanium detector lung counting systems. The function is applicable over the range of existing phantoms and the range of equipment types tested. Subtle differences between the detector systems are shown by differences in the fit parameters. This analysis could be a useful addition to lung counting analysis software. The LLNL and JAERI phantoms have very similar counting characteristics as evidenced by the similarity of the function parameters when measured using a single detector system. [ABSTRACT FROM AUTHOR]

Neyman-Pearson principles are briefly discussed and 95% confidence intervals of the form [0, ##.##] are presented. Use is made of the fact that the probability of the difference of two random variables, each with a Poisson distribution, can be expressed in terms of modified Bessel functions of integral order and elementary functions. The validity of the values is discussed. [ABSTRACT FROM AUTHOR]

Detection limits are presented for duplicate background samples thatproduced counting data with extra-Poisson variance that was attributed to a nonuniform activity distribution in the background sample medium. The presence of extra-Poisson variance was detected using the chi-squared test, where the presumed change in baseline activity from sample to sample was interpreted as an increase in experimental population variance. The runs test and Wilk-Shapiro test verified, respectively, the acceptable randomness of the data and the hypothesis that the data are normally distributed. Confidence intervals for detection limits therefore were based on the normal and t-distributions. The reduced chi-squared statistic was incorporated into the equations for the critical level and lower limit of detection to account for experimental variance beyond the expected Poisson value. The incorporation of extra-Poisson variance increased these detection limits for a well-defined background by a factor of 2.3 compared to the expected valuesfor the paired-sample method which were derived under the assumptionof Poisson variance, where the 30 background measurements have a reduced chi-squared statistic of 9.44. [ABSTRACT FROM AUTHOR]