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Title: SU-G-BRB-07: Developing a QA Procedure for Gated VMAT SABR Treatments Using 10 MV Beam in Flattening-Filter Free Mode

Abstract

Purpose: To develop a QA procedure for gated VMAT stereotactic ablative radiotherapy (SABR) treatments. Methods: An interface was constructed to attach the translational stage of a Quasar respiratory motion phantom to a pinpoint ion chamber insert and move the ion chamber inside an ArcCheck diode array. The Quasar phantom controller used a patient specific breathing pattern to translate the ion chamber in a superior-inferior direction inside the ArcCheck. An amplitude-based RPM tracking system was specified to turn the beam on during the exhale phase of the breathing pattern. SABR plans were developed using Eclipse for liver PTVs ranging in size from 3-12 cm in diameter using a 2-arc VMAT technique. Dose was measured in the middle of the penumbra region, where the high dose gradient allowed for sensitive detection of any inaccuracies in gated dose delivery. The overall fidelity of the dose distribution was confirmed using ArcCheck. The sensitivity of the gating QA procedure was investigated with respect to the following four parameters: PTV size, duration of exhale, baseline drift, and gating window size. Results: The difference between the measured dose to a point in the penumbra and the Eclipse calculated dose was under 2% for small residual motions. Themore » QA procedure was independent of PTV size and duration of exhale. Baseline drift and gating window size, however, significantly affected the penumbral dose measurement, with differences of up to 30% compared to Eclipse. Conclusion: This study described a highly sensitive QA procedure for gated VMAT SABR treatments. The QA outcome was dependent on the gating window size and baseline drift. Analysis of additional patient breathing patterns will be required to determine a clinically relevant gating window size and an appropriate tolerance level for this procedure.« less

Authors:
 [1];  [2];  [3]
  1. University of Victoria, Victoria, British Columbia (Canada)
  2. British Columbia Cancer Agency, Victoria, British Columbia (Canada)
  3. British Columbia Cancer Agency, Vancouver, British Columbia (Canada)
Publication Date:
OSTI Identifier:
22649279
Resource Type:
Journal Article
Journal Name:
Medical Physics
Additional Journal Information:
Journal Volume: 43; Journal Issue: 6; Other Information: (c) 2016 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:
60 APPLIED LIFE SCIENCES; 61 RADIATION PROTECTION AND DOSIMETRY; BEAMS; IONIZATION CHAMBERS; RADIATION DOSE DISTRIBUTIONS; RADIOTHERAPY; RESPIRATION; SENSITIVITY

Citation Formats

Chitsazzadeh, S, Wells, D, and Mestrovic, A. SU-G-BRB-07: Developing a QA Procedure for Gated VMAT SABR Treatments Using 10 MV Beam in Flattening-Filter Free Mode. United States: N. p., 2016. Web. doi:10.1118/1.4956914.
Chitsazzadeh, S, Wells, D, & Mestrovic, A. SU-G-BRB-07: Developing a QA Procedure for Gated VMAT SABR Treatments Using 10 MV Beam in Flattening-Filter Free Mode. United States. https://doi.org/10.1118/1.4956914
Chitsazzadeh, S, Wells, D, and Mestrovic, A. 2016. "SU-G-BRB-07: Developing a QA Procedure for Gated VMAT SABR Treatments Using 10 MV Beam in Flattening-Filter Free Mode". United States. https://doi.org/10.1118/1.4956914.
@article{osti_22649279,
title = {SU-G-BRB-07: Developing a QA Procedure for Gated VMAT SABR Treatments Using 10 MV Beam in Flattening-Filter Free Mode},
author = {Chitsazzadeh, S and Wells, D and Mestrovic, A},
abstractNote = {Purpose: To develop a QA procedure for gated VMAT stereotactic ablative radiotherapy (SABR) treatments. Methods: An interface was constructed to attach the translational stage of a Quasar respiratory motion phantom to a pinpoint ion chamber insert and move the ion chamber inside an ArcCheck diode array. The Quasar phantom controller used a patient specific breathing pattern to translate the ion chamber in a superior-inferior direction inside the ArcCheck. An amplitude-based RPM tracking system was specified to turn the beam on during the exhale phase of the breathing pattern. SABR plans were developed using Eclipse for liver PTVs ranging in size from 3-12 cm in diameter using a 2-arc VMAT technique. Dose was measured in the middle of the penumbra region, where the high dose gradient allowed for sensitive detection of any inaccuracies in gated dose delivery. The overall fidelity of the dose distribution was confirmed using ArcCheck. The sensitivity of the gating QA procedure was investigated with respect to the following four parameters: PTV size, duration of exhale, baseline drift, and gating window size. Results: The difference between the measured dose to a point in the penumbra and the Eclipse calculated dose was under 2% for small residual motions. The QA procedure was independent of PTV size and duration of exhale. Baseline drift and gating window size, however, significantly affected the penumbral dose measurement, with differences of up to 30% compared to Eclipse. Conclusion: This study described a highly sensitive QA procedure for gated VMAT SABR treatments. The QA outcome was dependent on the gating window size and baseline drift. Analysis of additional patient breathing patterns will be required to determine a clinically relevant gating window size and an appropriate tolerance level for this procedure.},
doi = {10.1118/1.4956914},
url = {https://www.osti.gov/biblio/22649279}, journal = {Medical Physics},
issn = {0094-2405},
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}
}