Calculational methods for estimating skin dose from electrons in Co-60 gamma-ray beams

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Abstract
Several methods were employed to calculate the relative contribution to skin dose [in humans] due to scattered electrons in 60Co .gamma.-rays beams. Either the Klein-Nishina differential scattering probability is employed to determine the number and initial energy of electrons scattered into the direction of a detector, or a Gaussian approximation is used to specify the surface distribution of initial pencil electron beams created by parallel or diverging photon fields. Results of these calculations are compared with experimental data. In addition, that fraction of relative surface dose resulting from photon interactions in air alone is estimated and compared with data extrapolated from measurements at large source-surface distance (SSD). The contribution to surface dose from electrons generated in air is .ltoreq. 50% of the total skin dose for SSD > 80 cm.
Funding Information
  • National Institute of Health (P01-CA19278)