Program Information
The Determination of Small Field Synthetic Single-Crystal Diamond Detector Correction Factors for Cyberknife, Gamma Knife Perfexion and Linear Accelerator
T Veselsky1,2,3*, V Pastykova1,2 , J Novotny1,2,3 , (1) Czech Technical University, Faculty of Nuclear Sciences and Physical Engineering, Prague 1, Czech Republic, (2) Na Homolce Hospital, Prague 5, Czech Republic, (3) Motol University Hospital, Prague 5, Czech Republic
Presentations
SU-F-108-8 (Sunday, July 30, 2017) 2:05 PM - 3:00 PM Room: 108
Purpose: Dosimetry of small radiation fields in radiotherapy and radiosurgery has become important and discussed issue in recent years. New small field dosimetric formalism has been published by Alfonso et al. This formalism includes use of the correction factors that need to be calculated using Monte Carlo or be measured for particular detector.
Methods: In this study, the correction factors for new synthetic single-crystal diamond detector (PTW 60019 MicroDiamond) were measured. Monte Carlo correction factors for Dosimetry Diode (PTW 60017) and Monte Carlo output factor data were used as reference. Small fields of Cyberknife, Gamma Knife Perfexion and Varian Clinac were investigated. The full range of Cyberknife fixed cones and Iris collimator (5 – 60 mm in diameter) were measured. Gamma Knife 4 mm and 8 mm collimators and Varian Clinac radiation fields from 10 cm down to 5 mm were used in this study.
Results: Synthetic single-crystal diamond detector was found to overestimate the output factor values (except for the smallest 5 mm radiation field where it underestimates the correct value) for Cyberknife fixed cones and Iris collimator. The correction factors for both collimation systems did not exceed 3% of the uncorrected output factor values. In case of Gamma Knife, the detector was positioned with its axis parallel and perpendicular to the couch axis. Both detector orientations showed overestimation of the detector response in comparison with Monte Carlo data. However, the correction factors for both collimator sizes were within 2% of the uncorrected output factor values. The correction factors for small fields of Varian Clinac accelerator were determined to be less than 1.5% even for the smallest field of 5 mm size.
Conclusion: New MicroDiamond detector was according to this study found to be suitable for relative dosimetry of small radiosurgery fields with the correction factors less than 3%.
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