Monte Carlo calculations of the dose backscatter factor for monoenergetic electrons. 1999

S H Cho, and W D Reece
Department of Nuclear Engineering, Texas A&M University, College Station 77843-3133, USA.

Recently, there has been growing interest in beta emitters for therapeutic uses, especially in connection with so-called endovascular (or intravascular) brachytherapy. Since accurate dose estimation is necessary for the success of such applications, some problems in beta-ray dosimetry need further study. Among these problems, we have investigated the effect of electron backscattering on dose, which has significance not only for accurate dose estimation but also for new source design. In this study, an empirical measure of electron backscattering, known as the dose backscatter factor, was calculated using EGS4 Monte Carlo calculations for monoenergetic electrons and various scattering materials. Electron energies were 0.1, 0.5, 1.0, 2.0 and 3.0 MeV in combination with Al (Z = 13), Ti (Z = 22), Sr (Z = 38), Ag (Z = 47) and Pt (Z = 78) scatterers. The dose backscatter factor ranged from 10% to 60%, depending on electron energy and material, and was found to increase with the atomic number Z by a log(Z + 1) relationship. A method is presented for calculating the beta-ray dose backscatter factors using the results of this study. To demonstrate the efficacy of this method, a dose backscatter factor depth profile for 32P near a water/aluminium interface was calculated and these calculated results were found to generally reproduce the depth profile obtained from direct EGS4 calculations using the 32P spectrum. The data presented in this study can be used to calculate dose backscatter factors for any combination of beta emitter/scatterer whose atomic number ranges from 13 to 78.

UI MeSH Term Description Entries
D009010 Monte Carlo Method In statistics, a technique for numerically approximating the solution of a mathematical problem by studying the distribution of some random variable, often generated by a computer. The name alludes to the randomness characteristic of the games of chance played at the gambling casinos in Monte Carlo. (From Random House Unabridged Dictionary, 2d ed, 1993) Method, Monte Carlo
D011879 Radiotherapy Dosage The total amount of radiation absorbed by tissues as a result of radiotherapy. Dosage, Radiotherapy,Dosages, Radiotherapy,Radiotherapy Dosages
D011880 Radiotherapy Planning, Computer-Assisted Computer-assisted mathematical calculations of beam angles, intensities of radiation, and duration of irradiation in radiotherapy. Computer-Assisted Radiotherapy Planning,Dosimetry Calculations, Computer-Assisted,Planning, Computer-Assisted Radiotherapy,Calculation, Computer-Assisted Dosimetry,Calculations, Computer-Assisted Dosimetry,Computer Assisted Radiotherapy Planning,Computer-Assisted Dosimetry Calculation,Computer-Assisted Dosimetry Calculations,Dosimetry Calculation, Computer-Assisted,Dosimetry Calculations, Computer Assisted,Planning, Computer Assisted Radiotherapy,Radiotherapy Planning, Computer Assisted
D001918 Brachytherapy A collective term for interstitial, intracavity, and surface radiotherapy. It uses small sealed or partly-sealed sources that may be placed on or near the body surface or within a natural body cavity or implanted directly into the tissues. Curietherapy,Implant Radiotherapy,Plaque Therapy, Radioisotope,Radioisotope Brachytherapy,Radiotherapy, Interstitial,Radiotherapy, Intracavity,Radiotherapy, Surface,Brachytherapy, Radioisotope,Interstitial Radiotherapy,Intracavity Radiotherapy,Radioisotope Plaque Therapy,Radiotherapy, Implant,Surface Radiotherapy,Therapy, Radioisotope Plaque
D003198 Computer Simulation Computer-based representation of physical systems and phenomena such as chemical processes. Computational Modeling,Computational Modelling,Computer Models,In silico Modeling,In silico Models,In silico Simulation,Models, Computer,Computerized Models,Computer Model,Computer Simulations,Computerized Model,In silico Model,Model, Computer,Model, Computerized,Model, In silico,Modeling, Computational,Modeling, In silico,Modelling, Computational,Simulation, Computer,Simulation, In silico,Simulations, Computer
D006801 Humans Members of the species Homo sapiens. Homo sapiens,Man (Taxonomy),Human,Man, Modern,Modern Man
D001610 Beta Particles High energy POSITRONS or ELECTRONS ejected from a disintegrating atomic nucleus. Beta Rays,Beta Radiation,Radiation, Beta,Beta Particle,Beta Radiations,Beta Ray,Particle, Beta,Particles, Beta,Radiations, Beta,Ray, Beta,Rays, Beta
D012542 Scattering, Radiation The diversion of RADIATION (thermal, electromagnetic, or nuclear) from its original path as a result of interactions or collisions with atoms, molecules, or larger particles in the atmosphere or other media. (McGraw-Hill Dictionary of Scientific and Technical Terms, 6th ed) Radiation Scattering,Radiation Scatterings,Scatterings, Radiation

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