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Backscatter dose perturbation at high atomic number interfaces in megavoltage photon beams
Author(s) -
Das Indra J.,
Kahn Faiz M.
Publication year - 1989
Publication title -
medical physics
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.473
H-Index - 180
eISSN - 2473-4209
pISSN - 0094-2405
DOI - 10.1118/1.596345
Subject(s) - backscatter (email) , photon , atomic number , physics , effective atomic number , photon energy , optics , dosimetry , computational physics , beam (structure) , atomic physics , range (aeronautics) , materials science , nuclear medicine , medicine , telecommunications , computer science , wireless , composite material
Most computer algorithms used clinically for photon beam treatment planning are unable to predict the effect of electron backscattering on dose distribution from high atomic number materials. It has been observed that there is a significant dose enhancement at such an interface. We define the dose enhancement in terms of backscatter dose factor (BSDF), which depends on the energy of the photon beam, thickness and width of the inhomogeneity, distance from the interface, and the atomic number of the inhomogeneity. For all energies studied, the dose fall‐off is initially very rapid and disappears beyond a few millimeters upstream from the interface. Empirically derived equations are presented for dose calculation at the interfaces of various media, including bone and soft tissue, for photon energies in the range of Co‐60 gamma rays to 24 MV x rays.