The estimation of dose factors for active marrow exposed to bone-seeking beta-emitters, such as ⁸⁹Sr and ⁹⁰Sr/⁹⁰Y (0 – 1.5 MeV and 0 – 2.4 MeV, respectively), is an important task of bone dosimetry. Monte Carlo simulations of electron – photon transport to calculate the active marrow doses are based on the geometrical modeling of bone structures. The model geometry should consist of accurate descriptions of spongiosa fine structure and cortical bone thickness (because of the high probability of low energy electron emission) as well as descriptions of bone macro-dimensions (because the maximum electron path length in spongiosa is about 5-9 mm). New computer tomography (CT) -based methods are widely applied to develop computational dosimetric phantoms. The advantage of the CT-based method is in high realism of the description of complex bone shape as well as in the possibility of an adequate description of bone microstructure with µCT. However, the method has a number of disadvantages, viz.: (1) the method is laborious and expensive; (2) the use of cadavers is associated with organizational difficulties; (3) one cadaver –based model can be non-representative and does not allow estimation of the uncertainties associated with individual variability of human anatomy; (4) cortical bone thickness is fixed based on the CT, for which resolution is worse than the measurand; (5) in practice, the limitation in voxel resolution of the computational phantom often results in narrowing down the strong points given by µCT because of an inadequate representation of the microstructure. Moreover, high individual variability of bone shapes and macro-dimensions negates the advantages of the above-mentioned high realism. The aim of the presented study is to elaborate the algorithm of parametric bone modeling, which allows for the generation of phantoms of hematopoietic bone segments based on known micro- and macro dimensions. We propose an approach that permits easy subdivision of bones into small segments, which may be described by simple-shape geometric figures with appropriate voxel resolution. Spongiosa structure (presented by a stochastic rod-like model and calibrated by literature-derived bone volume-to-total volume ratio) is covered by a homogenous cortical layer. All parameters of the proposed cadaver-free model can be obtained from the literature on morphometry and hystomorphometry. Moreover, the parametric modeling allows the simulation of individual variability of bone-specific dimensions.

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