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Analytical modeling of depth-dose degradation in heterogeneous lung tissue for intensity-modulated proton therapy planning

BACKGROUND AND PURPOSE: Proton therapy may be promising for treating non-small-cell lung cancer due to lower doses to the lung and heart, as compared to photon therapy. A reported challenge is degradation, i.e., a smoothing of the depth-dose distribution due to heterogeneous lung tissue. For pencil...

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Autores principales: Winter, Johanna, Ellerbrock, Malte, Jäkel, Oliver, Greilich, Steffen, Bangert, Mark
Formato: Online Artículo Texto
Lenguaje:English
Publicado: Elsevier 2020
Materias:
Acceso en línea:https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7807882/
https://www.ncbi.nlm.nih.gov/pubmed/33458311
http://dx.doi.org/10.1016/j.phro.2020.05.001
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author Winter, Johanna
Ellerbrock, Malte
Jäkel, Oliver
Greilich, Steffen
Bangert, Mark
author_facet Winter, Johanna
Ellerbrock, Malte
Jäkel, Oliver
Greilich, Steffen
Bangert, Mark
author_sort Winter, Johanna
collection PubMed
description BACKGROUND AND PURPOSE: Proton therapy may be promising for treating non-small-cell lung cancer due to lower doses to the lung and heart, as compared to photon therapy. A reported challenge is degradation, i.e., a smoothing of the depth-dose distribution due to heterogeneous lung tissue. For pencil beams, this causes a distal falloff widening and a peak-to-plateau ratio decrease, not considered in clinical treatment planning systems. MATERIALS AND METHODS: We present a degradation model implemented into an analytical dose calculation, fully integrated into a treatment planning workflow. Degradation effects were investigated on target dose, distal dose falloffs, and mean lung dose for ten patient cases with varying anatomical characteristics. RESULTS: For patients with pronounced range straggling (in our study large tumors, or lesions close to the mediastinum), degradation effects were restricted to a maximum decrease in target coverage (D(95) of the planning target volume) of 1.4%. The median broadening of the distal 80–20% dose falloffs was 0.5 mm at the maximum. For small target volumes deep inside lung tissue, however, the target underdose increased considerably by up to 26%. The mean lung dose was not negatively affected by degradation in any of the investigated cases. CONCLUSION: For most cases, dose degradation due to heterogeneous lung tissue did not yield critical organ at risk overdosing or overall target underdosing. However, for small and deep-seated tumors which can only be reached by penetrating lung tissue, we have seen substantial local underdose, which deserves further investigation, also considering other prevalent sources of uncertainty.
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spelling pubmed-78078822021-01-14 Analytical modeling of depth-dose degradation in heterogeneous lung tissue for intensity-modulated proton therapy planning Winter, Johanna Ellerbrock, Malte Jäkel, Oliver Greilich, Steffen Bangert, Mark Phys Imaging Radiat Oncol Original Research Article BACKGROUND AND PURPOSE: Proton therapy may be promising for treating non-small-cell lung cancer due to lower doses to the lung and heart, as compared to photon therapy. A reported challenge is degradation, i.e., a smoothing of the depth-dose distribution due to heterogeneous lung tissue. For pencil beams, this causes a distal falloff widening and a peak-to-plateau ratio decrease, not considered in clinical treatment planning systems. MATERIALS AND METHODS: We present a degradation model implemented into an analytical dose calculation, fully integrated into a treatment planning workflow. Degradation effects were investigated on target dose, distal dose falloffs, and mean lung dose for ten patient cases with varying anatomical characteristics. RESULTS: For patients with pronounced range straggling (in our study large tumors, or lesions close to the mediastinum), degradation effects were restricted to a maximum decrease in target coverage (D(95) of the planning target volume) of 1.4%. The median broadening of the distal 80–20% dose falloffs was 0.5 mm at the maximum. For small target volumes deep inside lung tissue, however, the target underdose increased considerably by up to 26%. The mean lung dose was not negatively affected by degradation in any of the investigated cases. CONCLUSION: For most cases, dose degradation due to heterogeneous lung tissue did not yield critical organ at risk overdosing or overall target underdosing. However, for small and deep-seated tumors which can only be reached by penetrating lung tissue, we have seen substantial local underdose, which deserves further investigation, also considering other prevalent sources of uncertainty. Elsevier 2020-05-26 /pmc/articles/PMC7807882/ /pubmed/33458311 http://dx.doi.org/10.1016/j.phro.2020.05.001 Text en © 2020 The Authors http://creativecommons.org/licenses/by-nc-nd/4.0/ This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/).
spellingShingle Original Research Article
Winter, Johanna
Ellerbrock, Malte
Jäkel, Oliver
Greilich, Steffen
Bangert, Mark
Analytical modeling of depth-dose degradation in heterogeneous lung tissue for intensity-modulated proton therapy planning
title Analytical modeling of depth-dose degradation in heterogeneous lung tissue for intensity-modulated proton therapy planning
title_full Analytical modeling of depth-dose degradation in heterogeneous lung tissue for intensity-modulated proton therapy planning
title_fullStr Analytical modeling of depth-dose degradation in heterogeneous lung tissue for intensity-modulated proton therapy planning
title_full_unstemmed Analytical modeling of depth-dose degradation in heterogeneous lung tissue for intensity-modulated proton therapy planning
title_short Analytical modeling of depth-dose degradation in heterogeneous lung tissue for intensity-modulated proton therapy planning
title_sort analytical modeling of depth-dose degradation in heterogeneous lung tissue for intensity-modulated proton therapy planning
topic Original Research Article
url https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7807882/
https://www.ncbi.nlm.nih.gov/pubmed/33458311
http://dx.doi.org/10.1016/j.phro.2020.05.001
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