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Characteristics of the photon beam from a new 25‐MV linear accelerator
Author(s) -
Aldrich John E.,
Andrew John W.,
Michaels Howard B.,
O'Brien Peter F.
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 - 10.1118/1.595763
Subject(s) - linear particle accelerator , photon , beam (structure) , physics , optics , particle accelerator , medical physics , nuclear physics
The Therac 25 is a relatively compact therapy machine, the heart of which is a double‐pass electron linear accelerator. The electron beam is injected into the accelerator at the treatment head end of the machine and is accelerated back down the arm to an energy of 13 MeV. At this end of the machine a magnet system reflects the beam back into the structure where it gains up to an additional 12 MeV of energy. After leaving the linear accelerator the beam is bent by an achromatic head magnet through 270° to the treatment head. The machine produces eight electron beams and a 25‐MV photon beam. In this work only the parameters of the photon beam are addressed based on measurements at the first two clinical sites. Percentage depth doses, tissue phantom ratios, and beam symmetry and stability are presented and discussed.