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Title: SU-C-201-06: Small Field Correction Factors for the MicroDiamond Detector in the Gamma Knife-Model C Derived Using Monte Carlo Methods

Abstract

Purpose: To determine small field correction factors for PTW’s microDiamond detector in Elekta’s Gamma Knife Model-C unit. These factors allow the microDiamond to be used in QA measurements of output factors in the Gamma Knife Model-C; additionally, the results also contribute to the discussion on the water equivalence of the relatively-new microDiamond detector and its overall effectiveness in small field applications. Methods: The small field correction factors were calculated as k correction factors according to the Alfonso formalism. An MC model of the Gamma Knife and microDiamond was built with the EGSnrc code system, using BEAMnrc and DOSRZnrc user codes. Validation of the model was accomplished by simulating field output factors and measurement ratios for an available ABS plastic phantom and then comparing simulated results to film measurements, detector measurements, and treatment planning system (TPS) data. Once validated, the final k factors were determined by applying the model to a more waterlike solid water phantom. Results: During validation, all MC methods agreed with experiment within the stated uncertainties: MC determined field output factors agreed within 0.6% of the TPS and 1.4% of film; and MC simulated measurement ratios matched physically measured ratios within 1%. The final k correction factors formore » the PTW microDiamond in the solid water phantom approached unity to within 0.4%±1.7% for all the helmet sizes except the 4 mm; the 4 mm helmet size over-responded by 3.2%±1.7%, resulting in a k factor of 0.969. Conclusion: Similar to what has been found in the Gamma Knife Perfexion, the PTW microDiamond requires little to no corrections except for the smallest 4 mm field. The over-response can be corrected via the Alfonso formalism using the correction factors determined in this work. Using the MC calculated correction factors, the PTW microDiamond detector is an effective dosimeter in all available helmet sizes. The authors would like to thank PTW (Friedberg, Germany) for providing the PTW microDiamond detector for this research.« less

Authors:
 [1];  [2];  [1];  [2]
  1. Wayne State University, Detroit, MI (United States)
  2. (United States)
Publication Date:
OSTI Identifier:
22624311
Resource Type:
Journal Article
Resource Relation:
Journal Name: Medical Physics; Journal Volume: 43; Journal Issue: 6; Other Information: (c) 2016 American Association of Physicists in Medicine; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
07 ISOTOPES AND RADIATION SOURCES; 60 APPLIED LIFE SCIENCES; CORRECTIONS; DOSEMETERS; FILMS; MONTE CARLO METHOD; PHANTOMS; VALIDATION

Citation Formats

Barrett, J C, Karmanos Cancer Institute McLaren-Macomb, Clinton Township, MI, Knill, C, and Beaumont Hospital, Canton, MI. SU-C-201-06: Small Field Correction Factors for the MicroDiamond Detector in the Gamma Knife-Model C Derived Using Monte Carlo Methods. United States: N. p., 2016. Web. doi:10.1118/1.4955546.
Barrett, J C, Karmanos Cancer Institute McLaren-Macomb, Clinton Township, MI, Knill, C, & Beaumont Hospital, Canton, MI. SU-C-201-06: Small Field Correction Factors for the MicroDiamond Detector in the Gamma Knife-Model C Derived Using Monte Carlo Methods. United States. doi:10.1118/1.4955546.
Barrett, J C, Karmanos Cancer Institute McLaren-Macomb, Clinton Township, MI, Knill, C, and Beaumont Hospital, Canton, MI. Wed . "SU-C-201-06: Small Field Correction Factors for the MicroDiamond Detector in the Gamma Knife-Model C Derived Using Monte Carlo Methods". United States. doi:10.1118/1.4955546.
@article{osti_22624311,
title = {SU-C-201-06: Small Field Correction Factors for the MicroDiamond Detector in the Gamma Knife-Model C Derived Using Monte Carlo Methods},
author = {Barrett, J C and Karmanos Cancer Institute McLaren-Macomb, Clinton Township, MI and Knill, C and Beaumont Hospital, Canton, MI},
abstractNote = {Purpose: To determine small field correction factors for PTW’s microDiamond detector in Elekta’s Gamma Knife Model-C unit. These factors allow the microDiamond to be used in QA measurements of output factors in the Gamma Knife Model-C; additionally, the results also contribute to the discussion on the water equivalence of the relatively-new microDiamond detector and its overall effectiveness in small field applications. Methods: The small field correction factors were calculated as k correction factors according to the Alfonso formalism. An MC model of the Gamma Knife and microDiamond was built with the EGSnrc code system, using BEAMnrc and DOSRZnrc user codes. Validation of the model was accomplished by simulating field output factors and measurement ratios for an available ABS plastic phantom and then comparing simulated results to film measurements, detector measurements, and treatment planning system (TPS) data. Once validated, the final k factors were determined by applying the model to a more waterlike solid water phantom. Results: During validation, all MC methods agreed with experiment within the stated uncertainties: MC determined field output factors agreed within 0.6% of the TPS and 1.4% of film; and MC simulated measurement ratios matched physically measured ratios within 1%. The final k correction factors for the PTW microDiamond in the solid water phantom approached unity to within 0.4%±1.7% for all the helmet sizes except the 4 mm; the 4 mm helmet size over-responded by 3.2%±1.7%, resulting in a k factor of 0.969. Conclusion: Similar to what has been found in the Gamma Knife Perfexion, the PTW microDiamond requires little to no corrections except for the smallest 4 mm field. The over-response can be corrected via the Alfonso formalism using the correction factors determined in this work. Using the MC calculated correction factors, the PTW microDiamond detector is an effective dosimeter in all available helmet sizes. The authors would like to thank PTW (Friedberg, Germany) for providing the PTW microDiamond detector for this research.},
doi = {10.1118/1.4955546},
journal = {Medical Physics},
number = 6,
volume = 43,
place = {United States},
year = {Wed Jun 15 00:00:00 EDT 2016},
month = {Wed Jun 15 00:00:00 EDT 2016}
}