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SU‐E‐T‐421: Commissioning of Brainlab Cones for 6×FFF and 10×FFF Beams On a Varian TrueBeam STx
Author(s) -
Wiant D,
Sintay B
Publication year - 2013
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 - 10.1118/1.4814855
Subject(s) - truebeam , physics , nuclear medicine , imaging phantom , beam (structure) , optics , linear particle accelerator , medicine
Purpose: To the best of our knowledge no data has been published on the use cones at 10×FFF and very little for 6×FFF. We report our experience commissioning and validating beam models for 4, 6, 7.5, 10, 12.5, and 15 mm cones on a Varian TrueBeam STx (Varian Medical Systems, Palo Alto, CA)). Methods: Scatter factors, radial profiles, and percent depth dose curves were measured per Brainlab protocol using a Sun Nuclear Edge Detector diode (Sun Nuclear Corp., Melboune, FL). The resulting Brainlab iPlan (Brainlab AG, Germany) beam models were validated with measurements of absolute dose and profiles at depths of 5, 10, and 15 cm in a polystyrene phantom using EBT3 radiochromic film (Ashland Inc., Covington, KY). Absolute doses were evaluated by comparing the average of pixels in the planned dose that had values > 80% of the maximum dose to the average of the corresponding pixels in the film. Results: The 6×FFF commissioning data was reviewed by Brainlab and found to be in good agreement with other user submitted data. Brainlab did not have a 10×FFF reference set at this time. The measured absolute dose agreed with planned dose to within 4.7% for all 6×FFF measurements (average difference of 2.1%) and within 4.9% for all 10×FFF measurements (average difference of 3.6%). Vertical and horizontal profiles through film planes gave full‐width‐at‐half‐maximum values that agreed with planned values to 0.4 mm for 6×FFF and to 0.2 mm for 10×FFF. Conclusion: The calculated dose distributions showed acceptable geometric agreement with measured values. The measured absolute dose for both energies was consistently lower than planned dose, with the difference more noticeable for the 10×FFF energy. This effect may be explained by reported over responses of diodes at small fields and under responses of EBT film at small fields.