Cookies on this website
We use cookies to ensure that we give you the best experience on our website. If you click 'Continue' we'll assume that you are happy to receive all cookies and you won't see this message again. Click 'Find out more' for information on how to change your cookie settings.

Electron backscatter at interfaces between dissimilar media can affect dosimetry and should be taken into consideration in radiotherapy and in radiobiology experiments. Backscatter dose perturbations depend upon factors such as electron energy, medium atomic number (Z), and distance from the interface. This study quantifies the backscatter dose factor (BSDF) for electron point sources of energy between 0.1 to 3 MeV in water at the interface with scattering materials ranging in Z from (13)Al to (79)Au. A Monte Carlo code that performs dose calculations for monoenergetic and continuous-spectrum electron sources was developed using EGSnrc transport routines. The BSDF was quantified in a parallel layers geometry (BSDF(1D)) and three-dimensional voxel geometry (BSDF(3D)). The BSDF(1D) near the interface increased up to 52% with decreasing energy from 3 to 0.1 MeV and increasing Z from 13 to 79. The analysis of the BSDF(3D) showed a significant dependence of the scattered electron angular distribution on Z and energy, with a decrease in isotropy going from high to low Z. This effect proves the importance of considering the correct geometry when quantifying the BSDF for electron sources, especially when the dimensions of the relevant dose-collecting volume are comparable with the CSDA range of the source.

Type

Journal article

Journal

Radiat Res

Publication Date

12/2004

Volume

162

Pages

693 - 701

Keywords

Electrons, Monte Carlo Method, Radiation Dosage, Scattering, Radiation