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SU‐E‐T‐536: SRS Diode and Diamond Detector Signal Response Correction Factors in Small Diameter Stereotactic Radiosurgery Fields
Author(s) -
Khelashvili G,
Chu J,
Bernard D,
Diaz A,
Turian J
Publication year - 2011
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 - 10.1118/1.3612498
Subject(s) - detector , optics , radiosurgery , physics , diamond , diode , truebeam , monte carlo method , dosimetry , linear particle accelerator , nuclear medicine , materials science , beam (structure) , optoelectronics , radiation therapy , mathematics , medicine , statistics , composite material
Purpose: To evaluate the magnitude of correction factors that need to be applied to the response of a SRS diode and a diamond detector used to measure the relative output factor of the 5.0 mm diameter BrainLab stereotactic cone in conjunction with a Varian Trilogy accelerator. Method and Materials: Required accuracy and precision in dose delivery during SRS can be achieved only when the geometric and dosimetric characteristics of the small radiation fields are completely understood. We have previously reported a 3% difference between the relative output factor (ROF) for the 5.0mm diameter cone measured with uncompensated Scanditronix/IBA Si‐ diode and ROF calculated by Monte Carlo simulations using MCSIM code. However, the reported values for ROF did not account for differences in response of Si under conditions lacking lateral electronic equilibrium. A Si‐ response correction factor has been calculated using MCSIM code and was applied to the measured value for ROF. In addition PTW 60003 diamond detector was used to verify previous measurements. Corrections for dose rate dependence and volume averaging have been made using MC simulations. Results: ROF obtained for SRS diode (0.683±0.011) and diamond detector (0.685±0.008) are in excellent agreement (within 0.2%) with each other and within 1–1.3% of previously reported MC calculated value of ROF (0.692±0.011). Conclusions: We have performed an experimental and theoretical investigation of ROF for radiation field created by BrainLab 5.0 mm SRS cone in conjunction with a Trilogy accelerator equipped with SRS mode. Methods of obtaining ROF using Scanditronix/IBA Si‐diode and PTW Diamond 60003 detector have been outlined. Monte Carlo simulations were used to correct for various effects contributing to potential detector response errors. We conclude that corrections for detector signal response up to ±4% were needed for both SRS diode and diamond detectors.