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SU‐FF‐T‐102: Clinical Beam Tuning of Low‐Energy Electron Beams: Matching Varian and Siemens Linear Accelerators
Author(s) -
O'Daniel J,
Kudchadker R,
Zullo J,
Gillin M
Publication year - 2007
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 - 10.1118/1.2760758
Subject(s) - linear particle accelerator , physics , beam (structure) , optics , siemens , cathode ray , electron , ionization chamber , monitor unit , percentage depth dose curve , range (aeronautics) , field size , nuclear medicine , nuclear physics , ion , materials science , ionization , composite material , quantum mechanics , medicine
Purpose: Tuning nominal energies on linear accelerators is useful for matching machines of different vendors and for altering energies to match clinical needs. In this study we investigated matching a Varian 2100EX 4MeV electron beam to a Siemens Primus 5MeV electron beam. Method and Materials: The 4MeV beam of a Varian 2100EX linear accelerator was tuned via a significant shunt‐voltage adjustment to match the 5MeV beam of a Siemens Primus linear accelerator. The percent depth‐depth dose (PDD) curves and off‐axis profiles for multiple field sizes were compared to validate the beam matching. Data was collected with a CC04 cylindrical chamber in water and with a parallel‐plate ion chamber in plastic water® (Computer Imaging Reference Systems, Inc., Norfolk, VA). Results: The PDD from the parallel‐plate and cylindrical ion chambers agreed within 1.1% and 2.5% for the 3×3cm 2 and 10×10cm 2 fields respectively. There was also good agreement in the PDD of the tuned 4MeV (referred to as 4MeV* post‐tuning) and 5MeV beams. The depth of D max was identical. Differences in the practical range were only 1mm. The PDD had the best agreement for the 3×3cm 2 field (⩽1.5% to depth of D 90 ), followed by the 10×10cm 2 field (⩽2.0% to depth of D 90 ) and the 25×25cm 2 field (⩽2.5% to depth of D 90 ). Larger disagreements occurred in the dose falloff region beyond D 90 , typically 2–7%. The off‐axis profiles for the 4MeV* and 5MeV beams showed good agreement for the 10×10cm 2 field (⩽2%). However, there was a substantial loss in flatness for the 25×25cm 2 field (5.5% for 4MeV*, 2.4% for 5MeV). We believe these differences are caused by the original 4MeV Varian scattering foil, which was not changed to reflect the greater energy of the 4MeV* beam. Conclusion: The Varian 4MeV and Siemens 5MeV beams were successfully matched, allowing oncologists to utilize these machines interchangeably.