title: SCALING PARAMETERS FOR HOT-PARTICLE BETA DOSIMETRY.
abstract: Scaling of dose-point kernel (DPK) values for beta particles transmitted by high-Z sources will overestimate dose at shallow depths while underestimating dose at greater depths due to spectral hardening. A new model has been developed based on a determination of the amount of monoenergetic electron absorption that occurs in a given source thickness through the use of EGSnrc (Electron Gamma Shower) Monte Carlo simulations. Integration over a particular beta spectrum provides the beta-particle DPK following self-absorption as a function of source thickness and radial depth in water, thereby accounting for spectral hardening that may occur in higher-Z materials. Beta spectra of varying spectral shapes and endpoint energies were used to test the model for select source materials with 7.42 ≤ Z ≤ 94. The results demonstrate that significant improvements can be made to DPK-based dosimetry models when dealing with high-Z volumetric sources. This new scaling model is currently being used to improve the accuracy of the beta-dosimetry calculations in VARSKIN 5.
authors.affiliation: St. Jude Children's Research Hospital, 262 Danny Thomas Place (MS 730), Memphis, TN 38105, USA colby.mangini@stjude.org.
authors.forename: Colby D
authors.initials: CD
authors.lastname: Mangini
authors.forename: David M
authors.initials: DM
authors.lastname: Hamby
mesh_terms: D001610:Beta Particles; D001918:Brachytherapy / Q000379:methods*; D003198:Computer Simulation; D004583:Electrons; D006801:Humans; D009010:Monte Carlo Method; D009369:Neoplasms / Q000532:radiotherapy*; D011874:Radiometry / Q000379:methods*; D011879:Radiotherapy Dosage; D011880:Radiotherapy Planning, Computer-Assisted / Q000379:methods*