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Measurement of the attenuation coefficient for livermore thoracic phantom lungs fabricated using contemporary materials.

Spitz-H; Glover-S; Liu-N; Smith-B; Hickman-D; Kruchten-D; Anderson-L
Health Phys 1994 Jul; 67(1):39-46
The performance characteristics of the Livermore Thoracic Phantom (LTP) lung model constructed of contemporary materials were evaluated. The LTP model was originally fabricated in 1978 to serve as a realistic consensus calibration standard for measuring plutonium (7440075) and other low energy gamma remitting radionuclides deposited in the respiratory tract. The University of Cincinnati reproduced the original formulation of the LTP model using a new polyurethane foam, calcium-carbonate, catalyst, and potassium-chloride (KCl). The KCl was introduced into the formulation to produce potassium-40 (K40) as an interfering radionuclide similar to that when a human subject is measured in- vivo. The materials when combined had a density of 0.26 gram per cubic meter and were intended to have a linear attenuation coefficient for plutonium with energies below 20 kiloelectron volts (keV) similar to that of human lungs. The ability of the University of Cincinnati fabricated LTP model (UC lungs) to perform to the standards of the original LTP model was assessed by determining linear attenuation coefficients for niobium-93m (Nb93m) X-rays delivered from a point source as they passed through the model. Representative linear attenuation coefficients for 16.6keV Nb93m X- rays through the UC lungs containing no KCl varied from 0.301 to 0.285. These values were comparable to those of the original model. For UC lungs that had been fabricated with 81 grams of KCl, the linear attenuation coefficients varied from 0.652 to 0.662, a more than two fold increase compared to the no KCl case. The authors conclude that phantom lung models for measuring attenuation characteristics of plutonium and other heavy actinides should be fabricated as close to the original LTP specifications as possible. Adding KCl to the materials to increase the K40 content is not necessary and may produce serious errors.
NIOSH-Author; Lung-tissue; Simulation-methods; Humans; Laboratory-equipment; Radioactive-metals; Radiation-exposure; Dosimetry
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