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Depth dose characteristics of elongated fields for electron beams from a 20‐MeV accelerator
Author(s) -
Sharma Subhash C.,
Wilson David L.
Publication year - 1985
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 - 10.1118/1.595703
Subject(s) - collimator , linear particle accelerator , flatness (cosmology) , electron , cathode ray , physics , dosimetry , particle accelerator , optics , range (aeronautics) , beam (structure) , nuclear physics , atomic physics , nuclear medicine , materials science , medicine , cosmology , quantum mechanics , composite material
In a Therac‐20 linear accelerator, 6–20 MeV electron beams are normally produced by shaping a scanned electron beam through primary x‐ray collimators and secondary electron trimmers. The collimator settings range continuously from 2 to 30 cm. Depth dose and field flatness parameters were measured for small elongated fields of the various electron energies. Depth dose of narrow fields defined either by the machine's collimator or lead cutouts agreed with data predicted from small square fields using the “square‐root” method.