Characteristics of contamination electrons in high energy photon beams.
A simple method to estimate the contribution of contaminating electrons to the dose, and to evaluate their dosimetric characteristics is proposed. The method is based on a normalisation of the tissue--maximum ratio curves to a constant primary photon fluence. The contribution of the contaminating electrons to the dose is calculated by subtracting the dose relative to a small field from the dose relative to the field under consideration. The method includes the determination of the mean energy, the linear apparent attenuation coefficient, the 50% range and the maximum range of the contaminating electrons. The extrapolated surface dose normalised to a constant primary photon fluence has been found to be constant for a constant collimator opening whatever may be the source distance.
Beauvais
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H
Physics Department, Insitut Gustabe Roussy, Villejuif, France.
Bridier
A
A
Dutreix
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A
D000042:Absorption; D004583:Electrons; D004735:Energy Transfer; D006801:Humans; D008954:Models, Biological; D008961:Models, Structural; D008962:Models, Theoretical; D010315:Particle Accelerators; D017785:Photons; D011879:Radiotherapy Dosage; D011882:Radiotherapy, High-Energy; D012542:Scattering, Radiation; D012867:Skin / Q000528:radiation effects*; D014965:X-Rays