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Feasibility and limitations of bulk density assignment in MRI for head and neck IMRT treatment planning
Head and neck cancers centered at the base of skull are better visualized on MRI than on CT. The purpose of this investigation was to investigate the accuracy of bulk density assignment in head and neck intensity‐modulated radiation therapy (IMRT) treatment plan optimization. Our study investigates...
Autores principales: | , , , |
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Formato: | Online Artículo Texto |
Lenguaje: | English |
Publicado: |
John Wiley and Sons Inc.
2014
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Materias: | |
Acceso en línea: | https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5711084/ https://www.ncbi.nlm.nih.gov/pubmed/25207571 http://dx.doi.org/10.1120/jacmp.v15i5.4851 |
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author | Chin, Alexander L. Lin, Alexander Anamalayil, Shibu Teo, Boon‐Keng Kevin |
author_facet | Chin, Alexander L. Lin, Alexander Anamalayil, Shibu Teo, Boon‐Keng Kevin |
author_sort | Chin, Alexander L. |
collection | PubMed |
description | Head and neck cancers centered at the base of skull are better visualized on MRI than on CT. The purpose of this investigation was to investigate the accuracy of bulk density assignment in head and neck intensity‐modulated radiation therapy (IMRT) treatment plan optimization. Our study investigates dose calculation differences between density‐assigned MRI and CT, and identifies potential limitations related to dental implants and MRI geometrical distortion in the framework of MRI‐only‐based treatment planning. Bulk density assignment was performed and applied onto MRI to generate three MRI image sets with increasing levels of heterogeneity for seven patients: 1) [Formula: see text]: all water‐equivalent; 2) [Formula: see text]: included bone with density of [Formula: see text]; and 3) [Formula: see text]: included bone and air. Using identical planning and optimization parameters, MRI‐based IMRT plans were generated and compared to corresponding, forward‐calculated, CT‐based plans on the basis of target coverage, isodose distributions, and dose‐volume histograms (DVHs). Phantom studies were performed to assess the magnitude and spatial dependence of MRI geometrical distortion. [Formula: see text] ‐based dose calculations overestimated target coverage by 16.1%. Segmentation of bone reduced differences to within 2% of the coverage area on the CT‐based plan. Further segmentation of air improved conformity near air–tissue interfaces. Dental artifacts caused substantial target coverage overestimation even on [Formula: see text]. Geometrical distortion was less than 1 mm in an imaging volume [Formula: see text] around scanner isocenter, but up to 4 mm at 17 cm lateral to isocenter. Bulk density assignment in the framework of MRI‐only IMRT head and neck treatment planning is a feasible method with certain limitations. Bone and teeth account for the majority of density heterogeneity effects. While soft tissue is well visualized on MRI compared to CT, dental implants may not be visible on MRI and must be identified by other means and assigned appropriate density for accurate dose calculation. Far off‐center geometrical distortion of the body contour near the shoulder region is a potential source of dose calculation inaccuracy. PACS numbers: 87.61.‐c, 87.55.‐D |
format | Online Article Text |
id | pubmed-5711084 |
institution | National Center for Biotechnology Information |
language | English |
publishDate | 2014 |
publisher | John Wiley and Sons Inc. |
record_format | MEDLINE/PubMed |
spelling | pubmed-57110842018-04-02 Feasibility and limitations of bulk density assignment in MRI for head and neck IMRT treatment planning Chin, Alexander L. Lin, Alexander Anamalayil, Shibu Teo, Boon‐Keng Kevin J Appl Clin Med Phys Radiation Oncology Physics Head and neck cancers centered at the base of skull are better visualized on MRI than on CT. The purpose of this investigation was to investigate the accuracy of bulk density assignment in head and neck intensity‐modulated radiation therapy (IMRT) treatment plan optimization. Our study investigates dose calculation differences between density‐assigned MRI and CT, and identifies potential limitations related to dental implants and MRI geometrical distortion in the framework of MRI‐only‐based treatment planning. Bulk density assignment was performed and applied onto MRI to generate three MRI image sets with increasing levels of heterogeneity for seven patients: 1) [Formula: see text]: all water‐equivalent; 2) [Formula: see text]: included bone with density of [Formula: see text]; and 3) [Formula: see text]: included bone and air. Using identical planning and optimization parameters, MRI‐based IMRT plans were generated and compared to corresponding, forward‐calculated, CT‐based plans on the basis of target coverage, isodose distributions, and dose‐volume histograms (DVHs). Phantom studies were performed to assess the magnitude and spatial dependence of MRI geometrical distortion. [Formula: see text] ‐based dose calculations overestimated target coverage by 16.1%. Segmentation of bone reduced differences to within 2% of the coverage area on the CT‐based plan. Further segmentation of air improved conformity near air–tissue interfaces. Dental artifacts caused substantial target coverage overestimation even on [Formula: see text]. Geometrical distortion was less than 1 mm in an imaging volume [Formula: see text] around scanner isocenter, but up to 4 mm at 17 cm lateral to isocenter. Bulk density assignment in the framework of MRI‐only IMRT head and neck treatment planning is a feasible method with certain limitations. Bone and teeth account for the majority of density heterogeneity effects. While soft tissue is well visualized on MRI compared to CT, dental implants may not be visible on MRI and must be identified by other means and assigned appropriate density for accurate dose calculation. Far off‐center geometrical distortion of the body contour near the shoulder region is a potential source of dose calculation inaccuracy. PACS numbers: 87.61.‐c, 87.55.‐D John Wiley and Sons Inc. 2014-09-08 /pmc/articles/PMC5711084/ /pubmed/25207571 http://dx.doi.org/10.1120/jacmp.v15i5.4851 Text en © 2014 The Authors. This is an open access article under the terms of the Creative Commons Attribution (http://creativecommons.org/licenses/by/3.0/) License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited. |
spellingShingle | Radiation Oncology Physics Chin, Alexander L. Lin, Alexander Anamalayil, Shibu Teo, Boon‐Keng Kevin Feasibility and limitations of bulk density assignment in MRI for head and neck IMRT treatment planning |
title | Feasibility and limitations of bulk density assignment in MRI for head and neck IMRT treatment planning |
title_full | Feasibility and limitations of bulk density assignment in MRI for head and neck IMRT treatment planning |
title_fullStr | Feasibility and limitations of bulk density assignment in MRI for head and neck IMRT treatment planning |
title_full_unstemmed | Feasibility and limitations of bulk density assignment in MRI for head and neck IMRT treatment planning |
title_short | Feasibility and limitations of bulk density assignment in MRI for head and neck IMRT treatment planning |
title_sort | feasibility and limitations of bulk density assignment in mri for head and neck imrt treatment planning |
topic | Radiation Oncology Physics |
url | https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5711084/ https://www.ncbi.nlm.nih.gov/pubmed/25207571 http://dx.doi.org/10.1120/jacmp.v15i5.4851 |
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