Return to search

Modified fermi-eyges electron scattering in tissue equivalent media

A theoretical and experimental study of the spatial spread of electron dose distributions for pencil and broad electron beams in various media is presented. We discuss in detail two methods for measurement of electron beam kinetic energies, describe our technique for the measurement of the optical density versus dose relationship for radiographic films, and present the experimental set-up for the measurement of the spatial spread of electron dose distributions for pencil and broad electron beams. / The Fermi-Eyges theory for the small angle multiple Coulomb scattering describes the spatial electron distribution in scattering media. The spatial spread of a pencil electron beam in a phantom as predicted by the Fermi-Eyges theory is an increasing function of depth in phantom irrespective of the depth. Our experiments, on the other hand, show that the spatial spread indeed increases with depth until depths close to 2/3 of the practical electron range, but at larger depths the spatial spread saturates, then decreases and vanishes at depths greater than the range of electrons in the material. To describe the observed saturation and the decrease of the spatial spread at depths beyond 2/3 of the practical electron range we introduce an electron absorption term containing four empirical parameters into the original Fermi differential equation and show that its solution describes the experimental results obtained for pencil electron beams of various energies in polystyrene, cork and aluminum phantoms. We also compare with experimental results the spatial electron dose distributions predicted by the Fermi-Eyges theory and the modified Fermi-Eyges theory for collimated broad electron beams.

Identiferoai:union.ndltd.org:LACETR/oai:collectionscanada.gc.ca:QMM.70178
Date January 1990
CreatorsBlais, Noël
PublisherMcGill University
Source SetsLibrary and Archives Canada ETDs Repository / Centre d'archives des thèses électroniques de Bibliothèque et Archives Canada
LanguageEnglish
Detected LanguageEnglish
TypeElectronic Thesis or Dissertation
Formatapplication/pdf
CoverageDoctor of Philosophy (Department of Physics.)
RightsAll items in eScholarship@McGill are protected by copyright with all rights reserved unless otherwise indicated.
Relationalephsysno: 001226763, proquestno: AAINN67581, Theses scanned by UMI/ProQuest.

Page generated in 0.0019 seconds