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SU‐E‐CAMPUS‐T‐06: Dose Perturbations by Electromagnetic Transponders in the Proton Environment
Author(s) -
Dolney D,
McDonough J,
Vapiwala N,
Metz J
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 - 10.1118/1.4815190
Subject(s) - transponder (aeronautics) , proton therapy , proton , beam (structure) , shadow (psychology) , physics , monte carlo method , optics , nuclear medicine , medicine , mathematics , nuclear physics , statistics , psychology , meteorology , psychotherapist
Purpose: Surgically implanted electromagnetic transponders have been used in external beamradiotherapy for target localization and position monitoring in real time. The effect of transponderson proton therapy dose distributions has not been reported. This study determines the level of thedose deficit that results from the presence of Calypso Beacon™ transponders in the path of thetreatment beam. Methods: A Monte Carlo implementation of the transponder geometry is validated against measurements using Gafchromic EBT2 film in a proton field and subsequently used to generate dosedistributions for transponders at different positions and orientations in the proton spread‐out Braggpeak. The maximum dose deficit is extracted in each case. Results: Dose shadows of up to 60% occur for transponders positioned very near the end ofrange of the Bragg peak. However, if transponders are positioned further than 5 mm from the endof range, and are not oriented parallel to the beam direction, then the dose deficit can be keptbelow 10%. Conclusion: Beacon electromagnetic transponders could be used for patient setup and motionmanagement for proton therapy provided some guidelines regarding their placement and orien‐tation with respect to the beam can be met. In cases of difficult transponder positions, optionsto minimise the shadow include careful plan design with multiple beam angles to distribute theshadow over a larger volume, or possibly increasing the dose in the expected shadow region tooffset the deficit.