Organ dose conversion coefficients for external photon irradiation of male and female voxel models

Abstract

New organ equivalent dose conversion coefficients are presented for whole body irradiation with monoenergetic photons of energies between 10 keV and 10 MeV for idealized geometries and seven adult male and female voxel models. The geometries are broad parallel photon beams in anterior-posterior, posterior-anterior, left- and right-lateral direction and a full 360 degree rotation around the body length axis. Dose differences between the different voxel models are below approximately 30% for some organs and geometries in the energy range between 60 and 200 keV, but they can be up to 100% or more in single cases, due to differences in stature and individual anatomical details. For low photon energies, the differences may amount to hundreds of per cent. Extensive comparisons of the dose conversion coefficients with respective values calculated using mathematical body models revealed various degrees of unrealistic positioning of single organs in the latter models. Examples are the kidneys, spleen and stomach that are located too superficially in the mathematical models. Over- or underestimations of several tens of per cent may, thus, occur for the mathematical models, compared to the voxel models considered. In contrast to previous assumptions, when the mathematical models have been used to establish reference organ dose conversion coefficients, it can be concluded that they do not properly represent a large population of individuals.

Incident air kerma to absorbed organ dose conversion factors for breast and lung in PA thorax radiography: The effect of patient thickness and radiation quality

“…Moreover, the reference values were calculated for the PCXMC phantom with standard dimensions, which corresponds to a patient size between XS and S (see Tables 1 and 2). For comparison, in the energy range between 60 and 200 keV, the range of variation in breast doses between different voxel models have been found to be up to 84% in the PA projection of whole body irradiations [31].…”

Reliability of Current Biokinetic and Dosimetric Models for Radionuclides: A Pilot Study

“…In that model the surface of the body is not represented in a realistic manner, and that may result in greater sensitivity to body size than the voxel models might indicate. As noted above, however, Zankl et al (2002) have observed dose differences as large as 100% among voxel models of adults. Calculations have not been reported for a sufficient number of voxel models of children to quantify the contribution of these anatomical models to uncertainties in the dose coefficients.…”

“…A voxel phantom is typically based on a living adult who is undergoing a scan for medical purposes but sometimes is based on a cadaver. Zankl et al (2002) used seven adult male and female voxel models to examine intersubject variability of tissue doses for external whole body irradiation by photons of energies between 10 keV and 10 MeV. The idealized geometries considered were broad parallel photon beams in anterior-posterior, posterior-anterior, left-and right-lateral direction and a full 360 degree rotation around the body length axis.…”

Voxel anthropomorphic phantoms: review of models used for ionising radiation dosimetry

“…There are other phantoms in the GSF library, but only partial information about these has so far been published. Helga (head to mid-thigh) and Irene (whole body) are two female adult phantoms and Frank (head and trunk) and Visible Human (head to knee) are two male adult phantoms (Petoussi-Henss et al, 2002;Zankl et al, 2002). A mode1 of the female digestive system has also been voxelized, as an important area from a dosimetric point of view, particularly for intemal exposure.…”

“…The authors of this work therefore recommend the use of voxel phantoms the size of whose organs is representative of the population under study, since the SAF is very dependent on the mass of the organs. For external dosimetry, the GSF team worked on establishing air kerma-to-dose conversion coefficients for exposure to photon beams in Baby and Child (especially for radiology examinations), Donna, Golem and Visible Human Zankl, 1992, 1993;Zankl et al, 1988Zankl et al, ,1995aZankl et al, , 1995bZankl et al, , 2002. The results were compared to those from the reference mathematical models from the new-born child, from the 10-year-old child , from Eva and from Adam.…”