Biomedical subjects

G L Catchen

Publications and source records attributed to G L Catchen.

3 recordsLinked to original sources

PubMed1990

Response of Panasonic dosimeters to submersion exposure by 133Xe.

The dose response to 133Xe radiation of several types of Panasonic 800 series thermoluminescent dosimeters (TLD) were evaluated. The dosimeters were exposed by submersion in 133Xe gas. The relative sensitivities of the lithium borate and the calcium sulfate phosphors were determined for several configurations. The TLDs were exposed in the holders (as the devices came from the vendor) with various shields covering the elements, and they were exposed with the TLDs removed from the holders. Some dosimeters were exposed, both in holders and out of holders (TL insert only configuration), both in plastic bags and free in air. For the in-holder configuration, the responses of the heavily shielded (greater than 170 mg cm-2) elements were used to obtain the photon dose-rate component, and the responses of the lightly shielded (less than 13 mg cm-2) element were used to obtain the beta component. Similarly, for the insert-only configurations, the observed over-response of the calcium sulfate phosphors to low-energy photons could be used to separate the beta dose rate component. By using the calculated beta doses, correction factors were determined for the apparent under-responses of the elements to beta radiation. The results of both methods are consistent. These results also suggest that the beta component could be used in environmental monitoring as a more sensitive means to determine 133Xe activities in clouds and to separate some of the effects of submersion exposure from those of distant exposure.

Atmosphere Exposure Chambers↗

PubMed1987

Experimental and computational techniques for beta-particle dosimetry.

This paper reports the experimental and the computational techniques that were specifically developed to provide dose response data for a new method of beta dosimetry, which is reported in an accompanying article (Sh87). The specific experimental techniques consist of setting up, calibrating and obtaining backscattering and resolution corrections for a plastic-scintillator-based beta spectrometer. The computation techniques involve (1) adapting a Monte Carlo electron transport computer code to use measured beta energy distributions as input data and (2) using the code to calculate the energy deposition of these distributions of electrons in a slab of material. The energy deposition of backscattered electrons incident on the slab is also taken into account. Codes, which were developed to calculate the energy deposited by photons in LiF, are used to derive a theoretical value for the TLD response calibration factor. This factor compares well to the experimentally derived result which was obtained by exposing TLDs to a calibrated 137Cs/137mBa photon source.

Algorithms↗

PubMed1987

An optimized computational method for determining the beta dose distribution using a multiple-element thermoluminescent dosimeter system.

This paper describes an optimization method for determining the beta dose distribution in tissue, and it describes the associated testing and verification. The method uses electron transport theory and optimization techniques to analyze the responses of a three-element thermoluminescent dosimeter (TLD) system. Specifically, the method determines the effective beta energy distribution incident on the dosimeter system, and thus the system performs as a beta spectrometer. Electron transport theory provides the mathematical model for performing the optimization calculation. In this calculation, parameters are determined that produce calculated doses for each of the chip/absorber components in the three-element TLD system. The resulting optimized parameters describe an effective incident beta distribution. This method can be used to determine the beta dose specifically at 7 mg X cm-2 or at any depth of interest. The doses at 7 mg X cm-2 in tissue determined by this method are compared to those experimentally determined using an extrapolation chamber. For a great variety of pure beta sources having different incident beta energy distributions, good agreement is found. The results are also compared to those produced by a commonly used empirical algorithm. Although the optimization method produces somewhat better results, the advantage of the optimization method is that its performance is not sensitive to the specific method of calibration.

Algorithms↗