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Title: SU-G-TeP1-12: Random Repainting as Mitigation for Scanned Ion Beam Interplay Effects

Abstract

Purpose: Interference of dose application in scanned beam particle therapy and organ motion may lead to interplay effects with distorted dose to target volumes. Interplay effects depend on the speed and direction of the scanning beam, leading to fringed field edges (scanning parallel to organ motion direction) or over- and under-dosed regions (both directions are orthogonal). Current repainting methods can mitigate interplay effects, but are susceptible to artefacts when only a limited number of repaints are applied. In this study a random layered-repainting strategy was investigated. Methods: Mono-energetic proton beams were irradiated to a 10 ×10 cm{sup 2} scanned field at a Varian ProBeam facility. Applied dose was measured with a 2D amorphous silicon detector mounted on a motion platform (CIRS dynamic platform). Motion was considered with different cycles, directions and translations up to ±8 mm. Dose distributions were measured for a static case, regular repainting (repeated meander-like path) and random repainting. Latter was realized by randomly distributing single spot locations during irradiation for a given number of repaints. Efficiency of repainting was analyzed by comparison to the static case. A simulation tool based on treatment logs and motion information was developed to compare measurement results to expected dose distributions.more » Results: Regular repainting could reduce motion artefacts, but dose distortion was strongly dependent on motion direction. Random repainting with same number of repaints (N=4) showed superior results, independent of target movement direction, while introducing slight penalty on delivery times, caused by an increase of overall scanning travel distance. The simulation tool showed good agreement to measured results. Conclusion: The results demonstrate significant improvement in terms of dose conformity when layered repainting is applied in a randomized fashion. This allows for reduced target margins during treatment planning and limited number of repaints. A combination with e.g. respiratory gating is straight-forward. Authors are employees of Varian Medical Systems Particle Therapy GmbH.« less

Authors:
;  [1]
  1. Varian Medical Systems Particle Therapy GmbH, Troisdorf, NRW (Germany)
Publication Date:
OSTI Identifier:
22649352
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:
43 PARTICLE ACCELERATORS; ION BEAMS; LOCAL IRRADIATION; MITIGATION; PROTON BEAMS; RADIATION DOSE DISTRIBUTIONS; RANDOMNESS

Citation Formats

Bach, M, and Wulff, J. SU-G-TeP1-12: Random Repainting as Mitigation for Scanned Ion Beam Interplay Effects. United States: N. p., 2016. Web. doi:10.1118/1.4957002.
Bach, M, & Wulff, J. SU-G-TeP1-12: Random Repainting as Mitigation for Scanned Ion Beam Interplay Effects. United States. doi:10.1118/1.4957002.
Bach, M, and Wulff, J. Wed . "SU-G-TeP1-12: Random Repainting as Mitigation for Scanned Ion Beam Interplay Effects". United States. doi:10.1118/1.4957002.
@article{osti_22649352,
title = {SU-G-TeP1-12: Random Repainting as Mitigation for Scanned Ion Beam Interplay Effects},
author = {Bach, M and Wulff, J},
abstractNote = {Purpose: Interference of dose application in scanned beam particle therapy and organ motion may lead to interplay effects with distorted dose to target volumes. Interplay effects depend on the speed and direction of the scanning beam, leading to fringed field edges (scanning parallel to organ motion direction) or over- and under-dosed regions (both directions are orthogonal). Current repainting methods can mitigate interplay effects, but are susceptible to artefacts when only a limited number of repaints are applied. In this study a random layered-repainting strategy was investigated. Methods: Mono-energetic proton beams were irradiated to a 10 ×10 cm{sup 2} scanned field at a Varian ProBeam facility. Applied dose was measured with a 2D amorphous silicon detector mounted on a motion platform (CIRS dynamic platform). Motion was considered with different cycles, directions and translations up to ±8 mm. Dose distributions were measured for a static case, regular repainting (repeated meander-like path) and random repainting. Latter was realized by randomly distributing single spot locations during irradiation for a given number of repaints. Efficiency of repainting was analyzed by comparison to the static case. A simulation tool based on treatment logs and motion information was developed to compare measurement results to expected dose distributions. Results: Regular repainting could reduce motion artefacts, but dose distortion was strongly dependent on motion direction. Random repainting with same number of repaints (N=4) showed superior results, independent of target movement direction, while introducing slight penalty on delivery times, caused by an increase of overall scanning travel distance. The simulation tool showed good agreement to measured results. Conclusion: The results demonstrate significant improvement in terms of dose conformity when layered repainting is applied in a randomized fashion. This allows for reduced target margins during treatment planning and limited number of repaints. A combination with e.g. respiratory gating is straight-forward. Authors are employees of Varian Medical Systems Particle Therapy GmbH.},
doi = {10.1118/1.4957002},
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}
}