title: A unified approach to photon and beta particle dosimetry.
abstract: The purpose of this investigation was to develop a unified and practical method for photon and beta particle dosimetry.
  
  
  METHODS
  This was achieved by developing a point-source function that is equally valid for photons and beta particles. This function contains four fitting parameters. These were computed on the basis of Berger's tables for a wide range of photon and beta particle energies. Explicit formulas were derived for the absorbed fraction within and outside of spheres containing a uniform distribution of activity. For photons, calculations of the absorbed fraction at the center of spheres were compared with the results of Monte Carlo calculations. The two methods yielded essentially identical results, validating the approach used in this study.
  
  
  RESULTS
  The results of this study show that there are absorbed-dose gradients as a function of distance from the center of a sphere. These should be taken into account in absorbed-dose calculations. For beta particles, it is shown explicitly that for spheres with a radius of 0.08 cm, absorbed-dose rates from 131I and 90Y beta particles are equal.
  
  
  CONCLUSIONS
  An important feature of this work is that calculations can be made on the macroscopic, cellular and subcellular levels. The approach employed and results obtained in this work should be particularly useful for tumor dosimetry in radionuclide therapy and applicable radiobiological investigations.
authors.affiliation: Department of Radiology, University of Nebraska Medical Center, Omaha 68198-1045.
authors.forename: P K
authors.initials: PK
authors.lastname: Leichner
mesh_terms: D001610:Beta Particles; D006801:Humans; D009010:Monte Carlo Method; D017785:Photons; D011829:Radiation Dosage; D011874:Radiometry / Q000379:methods*; D011879:Radiotherapy Dosage