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Tests of an electron monitor for routine quality control measurements of electron energies
Author(s) -
Ramsay E. B.,
Reinstein L. E.,
Meek A. G.
Publication year - 1991
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 - 10.1118/1.596598
Subject(s) - electron , cathode ray , detector , dosimetry , beam (structure) , physics , energy (signal processing) , particle accelerator , beam energy , materials science , atomic physics , optics , nuclear medicine , nuclear physics , medicine , quantum mechanics
The depth dose for electrons is sensitive to energy and the AAPM Task Group 24 has recommended that tests be performed at monthly intervals to assure electron beam energy constancy by verifying the depth for the 80% dose to within ±3 mm. Typically, this is accomplished by using a two‐depth dose ratio technique. Recently, a new device, the Geske monitor, has been introduced that is designed for verifying energy constancy in a single reading. The monitor consists of nine parallel plate detectors that alternate with 5‐mm‐thick absorbers made of an aluminum alloy. An evaluation of the clinical usefulness of this monitor for the electron beams available on a Varian Clinac 20 has been undertaken with respect to energy discrimination. Beam energy changes of 3 mm of the 80% dose give rise to measurable output changes ranging from 1.7% for 20‐MeV electron beams to 15% for 6‐MeV electron beams.