Radiation dose factors for alpha-emitters in osteons and some considerations on dose non-uniformity ratios and relative distribution factors.
Dose factors for locations within a tissue-filled cylindrical cavity bounded by an infinite medium of bone labelled with an alpha-emitter are calculated by means of a Monte Carlo procedure. The calculational approach is general and allows us to determine dose factors for specific distances or target volumes defined by concentric cylinders, as well as various source geometries including surface sources, buried surface sources, infinite and bounded volume sources, and also comprises plane (trabecular) surfaces as a limiting case. Values for the dose factors and the contribution of cross-fire traversals are calculated mainly for 239Pu and 226Ra and a typical Haversian canal diameter of 30 microns in beagles and 70 microns in humans. Also tables are given that allow dose factors to be derived for the relevant range of alpha-particle energies, diameters and target distances. The dose non-uniformity factors (local dose rate/average skeletal dose rate) for 239Pu are 27.2 in humans and 14.0 in beagles. The corresponding values for 226Ra are in the ranges 1.18-1.26 (humans) and 0.90-0.97 (beagles) for a 222Rn retention between 10-30%. The relative distribution factors 239Pu/226Ra are 21.5-23.0 for humans and 14.5-15.6 for dogs. General expressions for calculating non-uniformity factors and relative distribution factors are derived and implications are discussed in the light of some experimental findings.
Polig
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E
Radiobiology Division, University of Utah, Salt Lake City 84112.
D000512:Alpha Particles; D000818:Animals; D003198:Computer Simulation; D004285:Dogs; D006253:Haversian System / Q000528:radiation effects*; D006801:Humans; D008962:Models, Theoretical; D009010:Monte Carlo Method; D011005:Plutonium; D011829:Radiation Dosage; D011883:Radium
D011005:Plutonium; D011883:Radium