Measurement of the Attenuation Coefficient for Livermore Thoracic Phantom Lungs Fabricated Using Contemporary Materials

Abstract

The University of Cincinnati has reproduced the original formulation for the Livermore Thoracic Phantom lungs using contemporary materials and has adopted the linear attenuation coefficient as the primary quality assurance parameter for evaluating the performance capabilities of these new lung phantoms. The Livermore Thoracic Phantom was originally fabricated in 1978 to intercalibrate detector systems used to measure plutonium and other low-energy, photon emitting radionuclides deposited in the respiratory tract. The linear attenuation coefficient is a critical performance indicator for these phantom lungs since the presence of any material with a high effective atomic number (where Z > or = 20) will make a significant change in the photoelectric cross section, the predominant mode of interaction for plutonium x rays. A set of test lungs was fabricated with KCl to introduce a known quantity of 40K in the phantom and to determine, by measurement and calculations, what change would be made to the attenuation coefficient at photon energies below 100 keV as a result of the modified formulation. The KCl increased the linear attenuation coefficient below 60 keV by more than a factor of two, which would produce a substantial systematic error in any subsequent calibration measurements performed with these modified phantom lungs. These results support use of the attenuation coefficient as an important performance indicator for the Livermore Thoracic Phantom lungs and also suggest that KCl not be added to the lung tissue substitute formulation as a means to incorporate 40K in the phantom for low energy calibrations.

In Vivo Measurement of 241Am in the Lungs Confounded by Activity Deposited in Other Organs

“…Efficiency was determined by measuring the Livermore Torso Phantom containing precisely known quantities of 241 Am in the liver, lungs, and axillary lymph nodes (Spitz et al 1994;Spitz and Lodwick 2000;Zeman et al 2009). A head phantom, fabricated at the University of Cincinnati by Kellar (1995), containing 241 Am applied on the inner and outer surfaces of an imbedded skull, was measured to determine activity in the skeleton.…”

Influence of Manufacturing Processes on the Performance of Phantom Lungs

“…Other authors have stated that their lung densities may range from 0.25 to 0.3 g cm -3 (Fry and Summerling 1982;Griffith et al 1979). Spitz et al (1994) do not state the densities of their lung tissue substitute but do indicate a 7% difference in linear attenuation coefficients for two lungs. If the slopes of the relative brightness line are identical for all lung tissue substitutes, this would imply a 9 to 16% difference in the brightness of the lungs, depending on the manufacturer.…”

Utilisation des fantômes numériques voxélisés pour l'amélioration des étalonnages en anthroporadiamétrie pulmonaire

“…Des difficultés ont déjà été rencontrées sur les poumons et sont sans doute liées à la méthode de fabrication de ces derniers, qui consiste en un mélange manuel des radionucléides dans la mousse (Spitz et al, 1994 ;Kramer et Hauck, 2000 concerne la densité, des écarts de près de 40 % sont constatés entre les poumons contenant du 235 U enrichi à 3 % et les autres jeux de poumons ; il est intéressant de noter que ces différences peuvent être corrélées avec le fournisseur de ces poumons, les poumons « MOX » et uranium enrichi à 93 % n'ayant pas été fabriqués par la même société que les poumons uranium enrichi à 3 %. Par ailleurs, un écart de 15 % entre les poumons contenant uniquement du 235 U enrichi à 3 % et les poumons « MOX » a également pu être constaté sur l'efficacité du principal pic photoélectrique à 185,72 keV.…”