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Title: SU-E-T-359: Measurement of Various Metrics to Determine Changes in Megavoltage Photon Beam Energy

Abstract

Purpose: To examine the relationship between photon beam energy and various metrics for energy on the flattened and flattening filter free (FFF) beams generated by the Varian TrueBeam. Methods: Energy changes were accomplished by adjusting the bending magnet current ±10% from the nominal value for the 4, 6, 8, and 10 MV flattened and 6 and 10 MV FFF beams. Profiles were measured for a 30×30 cm{sup 2} field using a 2D ionization chamber array and a 3D water Scanner which was also used to measure PDDs. For flattened beams we compared several energy metrics; PDD at 10 cm depth in water (PDD(10)); the variation over the central 80% of the field (Flat); and the average of the highest reading along each diagonal divided by the CAX value, diagonal normalized flatness (FDN). For FFF beams we examined PDD(10), FDN, and the width of a chosen isodose level in a 30×30 cm{sup 2} field (W(d%)). Results: Changes in PDD(10) were nearly linear with changes in energy for both flattened and FFF beams as were changes in FDN. Changes in W(d%) were also nearly linear with energy for the FFF beams. PDD(10) was not as sensitive to changes in energy compared tomore » the other metrics for either flattened or FFF beams. Flat was not as sensitive to changes in energy compared to FDN for flattened beams and its behavior depends on depth. FDN was the metric that had the highest sensitivity to the changes in energy for flattened beams while W(d%) was the metric that had highest sensitivity to the changes in energy for FFF beams. Conclusions: The metric FDN was found to be most sensitive to energy changes for flattened beams, while the W(d%) was most sensitive to energy changes for FFF beams.« less

Authors:
 [1];  [2]; ;  [3]
  1. MD Anderson Cancer Ctr., Houston, TX (United States)
  2. UT MD Anderson Cancer Center, Houston, TX (United States)
  3. Sun Nuclear Corp, Melbourne, FL (Australia)
Publication Date:
OSTI Identifier:
22355906
Resource Type:
Journal Article
Journal Name:
Medical Physics
Additional Journal Information:
Journal Volume: 41; Journal Issue: 6; Other Information: (c) 2014 American Association of Physicists in Medicine; Country of input: International Atomic Energy Agency (IAEA); Journal ID: ISSN 0094-2405
Country of Publication:
United States
Language:
English
Subject:
07 ISOTOPES AND RADIATION SOURCES; BEAM PROFILES; DEPTH DOSE DISTRIBUTIONS; IONIZATION CHAMBERS; METRICS; PHOTON BEAMS

Citation Formats

Gao, S, Balter, P, Rose, M, and Simon, W. SU-E-T-359: Measurement of Various Metrics to Determine Changes in Megavoltage Photon Beam Energy. United States: N. p., 2014. Web. doi:10.1118/1.4888692.
Gao, S, Balter, P, Rose, M, & Simon, W. SU-E-T-359: Measurement of Various Metrics to Determine Changes in Megavoltage Photon Beam Energy. United States. https://doi.org/10.1118/1.4888692
Gao, S, Balter, P, Rose, M, and Simon, W. 2014. "SU-E-T-359: Measurement of Various Metrics to Determine Changes in Megavoltage Photon Beam Energy". United States. https://doi.org/10.1118/1.4888692.
@article{osti_22355906,
title = {SU-E-T-359: Measurement of Various Metrics to Determine Changes in Megavoltage Photon Beam Energy},
author = {Gao, S and Balter, P and Rose, M and Simon, W},
abstractNote = {Purpose: To examine the relationship between photon beam energy and various metrics for energy on the flattened and flattening filter free (FFF) beams generated by the Varian TrueBeam. Methods: Energy changes were accomplished by adjusting the bending magnet current ±10% from the nominal value for the 4, 6, 8, and 10 MV flattened and 6 and 10 MV FFF beams. Profiles were measured for a 30×30 cm{sup 2} field using a 2D ionization chamber array and a 3D water Scanner which was also used to measure PDDs. For flattened beams we compared several energy metrics; PDD at 10 cm depth in water (PDD(10)); the variation over the central 80% of the field (Flat); and the average of the highest reading along each diagonal divided by the CAX value, diagonal normalized flatness (FDN). For FFF beams we examined PDD(10), FDN, and the width of a chosen isodose level in a 30×30 cm{sup 2} field (W(d%)). Results: Changes in PDD(10) were nearly linear with changes in energy for both flattened and FFF beams as were changes in FDN. Changes in W(d%) were also nearly linear with energy for the FFF beams. PDD(10) was not as sensitive to changes in energy compared to the other metrics for either flattened or FFF beams. Flat was not as sensitive to changes in energy compared to FDN for flattened beams and its behavior depends on depth. FDN was the metric that had the highest sensitivity to the changes in energy for flattened beams while W(d%) was the metric that had highest sensitivity to the changes in energy for FFF beams. Conclusions: The metric FDN was found to be most sensitive to energy changes for flattened beams, while the W(d%) was most sensitive to energy changes for FFF beams.},
doi = {10.1118/1.4888692},
url = {https://www.osti.gov/biblio/22355906}, journal = {Medical Physics},
issn = {0094-2405},
number = 6,
volume = 41,
place = {United States},
year = {Sun Jun 01 00:00:00 EDT 2014},
month = {Sun Jun 01 00:00:00 EDT 2014}
}