<abstract xmlns="http://www.w3.org/1999/xhtml"><p>Shielded silicon diodes are commonly employed in commissioning of Cyberknife 6 MV photon beams. This study aims to measure output factors, off centered ratio (OCR), percentage depth dose (PDD) of 6 MV photons using shielded and unshielded diodes and to compare with Gafchromic EBT3 film measurements to investigate whether EBT3 could effectively characterize small 6 MV photon beams. Output factors, OCR and PDD were measured with shielded and unshielded silicon detectors in a radiation field analyzer system at reference condition. Water equivalent solid phantom were used while irradiating EBT3 films. From multiuser data, diodes underestimated output factor by 3% for collimator fields ≤ 10 mm, while EBT3 underestimated the output factor by 3.9% for 5 mm collimator. 1D Gamma analysis of OCR between diode and film, results in gamma ≤ 1 for all measured points with 1 mm distance to agreement (DTA) and 1% relative dose difference (DD). Dose at surface is overestimated with diodes compared to EBT3. PDD results were within 2% relative dose values between diode and EBT3 except for 5 mm collimator. Except for small collimator fields of up to 10 mm, results of output factor, OCR, PDD of all detectors used in this study exhibited similar results. Relative dose measurements with Gafchromic EBT3 in this work show that EBT3 films can be used effectively as an independent tool to verify commissioning beam data of small fields only after careful verification of methodology for any systematic errors with appropriate readout procedure.</p></abstract>

Shielded silicon diodes are commonly employed in commissioning of Cyberknife 6 MV photon beams. This study aims to measure output factors, off centered ratio (OCR), percentage depth dose (PDD) of 6 MV photons using shielded and unshielded diodes and to compare with Gafchromic EBT3 film measurements to investigate whether EBT3 could effectively characterize small 6 MV photon beams. Output factors, OCR and PDD were measured with shielded and unshielded silicon detectors in a radiation field analyzer system at reference condition. Water equivalent solid phantom were used while irradiating EBT3 films. From multiuser data, diodes underestimated output factor by 3% for collimator fields ≤ 10 mm, while EBT3 underestimated the output factor by 3.9% for 5 mm collimator. 1D Gamma analysis of OCR between diode and film, results in gamma ≤ 1 for all measured points with 1 mm distance to agreement (DTA) and 1% relative dose difference (DD). Dose at surface is overestimated with diodes compared to EBT3. PDD results were within 2% relative dose values between diode and EBT3 except for 5 mm collimator. Except for small collimator fields of up to 10 mm, results of output factor, OCR, PDD of all detectors used in this study exhibited similar results. Relative dose measurements with Gafchromic EBT3 in this work show that EBT3 films can be used effectively as an independent tool to verify commissioning beam data of small fields only after careful verification of methodology for any systematic errors with appropriate readout procedure.

Can Gafchromic EBT3 films effectively characterize small fields of 6 MV unflattened photon beams of Cyberknife system?

Central Physics, Department of Radiation Oncology

Polish Journal of Medical Physics and Engineering

This work is licensed under the Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 License.

Shielded silicon diodes are commonly employed in commissioning of Cyberknife 6 MV photon beams. This study aims to measure output factors, off centered ratio...

Can Gafchromic EBT3 films effectively characterize small fields of 6 MV unflattened photon beams of Cyberknife system?

Published Online: Dec 24, 2018

Page range: 181 - 187

Received: Jan 27, 2018

Accepted: Aug 09, 2018

DOI: https://doi.org/10.2478/pjmpe-2018-0025

Keywords
diode detectors, GafChromic EBT3, small fields, output factor, off centered ratio, percentage depth dose

© 2018 Jerrin Amalraj et al., published by Sciendo

This work is licensed under the Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 License.

Can Gafchromic EBT3 films effectively characterize small fields of 6 MV unflattened photon beams of Cyberknife system?

Published Online: Dec 24, 2018

Page range: 181 - 187

Received: Jan 27, 2018

Accepted: Aug 09, 2018

DOI: https://doi.org/10.2478/pjmpe-2018-0025

Keywordsdiode detectors, GafChromic EBT3, small fields, output factor, off centered ratio, percentage depth dose

© 2018 Jerrin Amalraj et al., published by Sciendo

This work is licensed under the Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 License.

Keywords
diode detectors, GafChromic EBT3, small fields, output factor, off centered ratio, percentage depth dose