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Microdosimetric single‐event spectra for megavoltage electrons
Author(s) -
Zellmer D. L.,
Amols H. I.
Publication year - 1990
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 - 10.1118/1.596490
Subject(s) - electron , spectral line , photon , dosimetry , radiation , atomic physics , physics , linear particle accelerator , relative biological effectiveness , nuclear medicine , nuclear physics , optics , medicine , beam (structure) , astronomy
Experimental techniques have been developed for obtaining single‐event microdosimetric spectra from hospital based linear accelerators. Therapeutic electrons of 12, 15, 18, and 20 MeV from Clinic 18 and 20 accelerators have been produced at ultralow dose rates. Details of the experimental methods have been described previously by the authors. Single‐event lineal energy spectra for these beams, as measured by a Rossi chamber differ significantly from cobalt‐60 both in shape and dose average lineal energy ( y ̄ d ) which, depending on electron energy, can be 20–40% lower. The spectral peaks for electrons are greatly enhanced compared to cobalt. The y ̄ d for electrons also differs from previously reported values for 10–15‐MV photon beams. These differences are less pronounced than for differences with cobalt. Spectral peaks and shapes correlate well with the actual electron stopping powers in tissue. The theory of dual radiation action predicts changes in relative biological effectiveness at low doses for megavoltage photon and electrons. Although at clinical doses the predicted differences are not statistically significant.