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Title: SU-E-T-653: Quantifying Inter-Fraction Range Uncertainty for Input Into Robust Proton Planning

Abstract

Purpose: To provide a method for quantifying centre- and tumour site-specific population range uncertainty due to inter-fraction motion for use within robust proton planning and plan analysis. PTV-based and probabilistic/robust plans depend upon accurate knowledge of geometric and range uncertainties. If the uncertainty model is inaccurate, both types of plan, PTV or probabilistic, could produce under-dosing of the target and/or overdosing of OAR. Methods: Daily mega-voltage volumetric imaging data from previously treated radiotherapy patients has been used to investigate inter-fraction changes to water equivalent path-length (WEPL). Daily image-guidance scans were carried out for each patient and corrected for changes in CTV position (using rigid transformations). An effective depth algorithm was used to determine residual range changes, after corrections were applied, by comparing WEPL within the CTV at each fraction for several beam angles. This method has been demonstrated for nine prostate and seven head and neck. Results: Inter-fraction range changes for the head and neck patient sample were Σ=3.39mm, σ=4.72mm and overall mean =−1.82mm; for prostate Σ=5.64mm, σ=5.91mm and overall mean =0.98 mm. The choice of beam angle for head and neck did not affect the inter-fraction range error significantly; however this was not the same for prostate. Greater rangemore » changes were seen using a lateral beam compared to an anterior beam for prostate due to relative motion of the prostate and femoral heads. Conclusion: A method has been developed to quantify population range changes due to inter-fraction motion. The results show a non-zero mean for these samples, as well as significant Σ and σ, highlighting the importance of quantifying uncertainties and use of image guidance. Such information can be used in robust optimisation algorithms and for analysing treatment plan robustness. It may also help in establishing beam start conditions at planning and for establishing adaptive planning protocols.« less

Authors:
;  [1];  [2];  [3]
  1. University of Cambridge, Cambridge (United Kingdom)
  2. University of Bristol, Bristol (United Kingdom)
  3. Cambridge University Hospitals, Cambridge (United Kingdom)
Publication Date:
OSTI Identifier:
22538162
Resource Type:
Journal Article
Resource Relation:
Journal Name: Medical Physics; Journal Volume: 42; Journal Issue: 6; Other Information: (c) 2015 American Association of Physicists in Medicine; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
62 RADIOLOGY AND NUCLEAR MEDICINE; BEAM POSITION; BIOMEDICAL RADIOGRAPHY; HEAD; NECK; NEOPLASMS; PATIENTS; PROBABILISTIC ESTIMATION; PROSTATE; PROTONS; RADIOTHERAPY

Citation Formats

McGowan, S, Burnet, N, Holloway, M, and Thomas, S. SU-E-T-653: Quantifying Inter-Fraction Range Uncertainty for Input Into Robust Proton Planning. United States: N. p., 2015. Web. doi:10.1118/1.4925016.
McGowan, S, Burnet, N, Holloway, M, & Thomas, S. SU-E-T-653: Quantifying Inter-Fraction Range Uncertainty for Input Into Robust Proton Planning. United States. doi:10.1118/1.4925016.
McGowan, S, Burnet, N, Holloway, M, and Thomas, S. Mon . "SU-E-T-653: Quantifying Inter-Fraction Range Uncertainty for Input Into Robust Proton Planning". United States. doi:10.1118/1.4925016.
@article{osti_22538162,
title = {SU-E-T-653: Quantifying Inter-Fraction Range Uncertainty for Input Into Robust Proton Planning},
author = {McGowan, S and Burnet, N and Holloway, M and Thomas, S},
abstractNote = {Purpose: To provide a method for quantifying centre- and tumour site-specific population range uncertainty due to inter-fraction motion for use within robust proton planning and plan analysis. PTV-based and probabilistic/robust plans depend upon accurate knowledge of geometric and range uncertainties. If the uncertainty model is inaccurate, both types of plan, PTV or probabilistic, could produce under-dosing of the target and/or overdosing of OAR. Methods: Daily mega-voltage volumetric imaging data from previously treated radiotherapy patients has been used to investigate inter-fraction changes to water equivalent path-length (WEPL). Daily image-guidance scans were carried out for each patient and corrected for changes in CTV position (using rigid transformations). An effective depth algorithm was used to determine residual range changes, after corrections were applied, by comparing WEPL within the CTV at each fraction for several beam angles. This method has been demonstrated for nine prostate and seven head and neck. Results: Inter-fraction range changes for the head and neck patient sample were Σ=3.39mm, σ=4.72mm and overall mean =−1.82mm; for prostate Σ=5.64mm, σ=5.91mm and overall mean =0.98 mm. The choice of beam angle for head and neck did not affect the inter-fraction range error significantly; however this was not the same for prostate. Greater range changes were seen using a lateral beam compared to an anterior beam for prostate due to relative motion of the prostate and femoral heads. Conclusion: A method has been developed to quantify population range changes due to inter-fraction motion. The results show a non-zero mean for these samples, as well as significant Σ and σ, highlighting the importance of quantifying uncertainties and use of image guidance. Such information can be used in robust optimisation algorithms and for analysing treatment plan robustness. It may also help in establishing beam start conditions at planning and for establishing adaptive planning protocols.},
doi = {10.1118/1.4925016},
journal = {Medical Physics},
number = 6,
volume = 42,
place = {United States},
year = {Mon Jun 15 00:00:00 EDT 2015},
month = {Mon Jun 15 00:00:00 EDT 2015}
}