Variable planning margin approach to account for locoregional variations in setup uncertainties.
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| Title: | Variable planning margin approach to account for locoregional variations in setup uncertainties. |
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| Authors: | Yang, Jinzhong1, Garden, Adam S.2, Zhang, Yongbin1, Zhang, Lifei1, Dong, Lei1 |
| Source: | Medical Physics. Aug2012, Vol. 39 Issue 8, p5136-5144. 9p. |
| Subjects: | Cancer radiotherapy, Head & neck cancer treatment, Cancer tomography, Medical protocols, Image registration, Gaussian processes |
| Abstract: | Purpose: To develop a method for creating variable planning margins around a clinical treatment volume (CTV) and to evaluate its application in head and neck cancer radiotherapy in accounting for locoregional variations of nonrigid setup uncertainties. Methods: Ten computed tomography (CT) images (with a resolution of 0.68 × 0.68 × 2.5 mm3) of a head and neck cancer patient were acquired from the first two weeks of treatment for this study. Five rigid structures (the C2, C5, and caudal C7 vertebrae, mandible, and jugular notch) were used as the landmarks for creating variable local margins. At different CTV locations, local margins were calculated as the weighted average of margins determined at different landmark points from previous studies. The weight was determined by a Gaussian falloff function of the distance between the current location and each landmark point. The CTV delineated on the planning CT image, spanning from the upper portion of the mouth to the lower part of the neck, was expanded to form the planning treatment volume (PTV) with either variable or the conventional constant margins. To evaluate the target coverage, the original planning CTV was deformably mapped to each daily treatment CT using a deformable image registration method. We examined the overlap of the deformed CTV and the rigidly aligned PTV for each margin design strategy and compared the efficacy of the variable margin with the constant margin approach. Results: For the variable margin approach with a baseline C2 margin of 2.5 mm in the left-right, anterior-posterior, and superior-inferior directions, an average of 99.2% of the CTV was within the PTV, and for the approach with a constant 2.5 mm margin, an average of 97.9% of the CTV was within the PTV. With a baseline margin of 2.0 mm, the variable margin approach had an average coverage of 97.8%, similar to that of the constant 2.5 mm margin approach. However, its average nonoverlapped PTV proportion was 32.4%, smaller than that of the constant 2.5 mm margin approach (33.7%). Paired t-tests of computations from the ten treatment fractions showed no significant difference in CTV coverage for the variable margin approach with a baseline of 2.0 mm and the constant 2.5 margin approach (p = 0.054), but the nonoverlapped PTV proportion was significantly smaller for the variable margin approach with a baseline of 2.0 mm than for the constant 2.5 mm margin approach (p < 0.0001). The CTV coverage with the variable margin approach was also significantly higher than with the constant margin approach in the lower neck area, where a larger setup error normally occurs. Conclusions: We implemented a variable margin approach to account for locoregional variations of setup uncertainties for head and neck cancer radiotherapy, and demonstrated the effectiveness of this approach when compared with the conventional global constant margin expansion approach, where the treatment target spreads out to a broad region. As variable margin data become available and more clinical studies are performed, this approach could be applicable to other treatment sites as well. [ABSTRACT FROM AUTHOR] |
| Copyright of Medical Physics is the property of Wiley-Blackwell and its content may not be copied or emailed to multiple sites without the copyright holder's express written permission. Additionally, content may not be used with any artificial intelligence tools or machine learning technologies. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.) | |
| Database: | Engineering Source |
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| Items | – Name: Title Label: Title Group: Ti Data: Variable planning margin approach to account for locoregional variations in setup uncertainties. – Name: Author Label: Authors Group: Au Data: <searchLink fieldCode="AR" term="%22Yang%2C+Jinzhong%22">Yang, Jinzhong</searchLink><relatesTo>1</relatesTo><br /><searchLink fieldCode="AR" term="%22Garden%2C+Adam+S%2E%22">Garden, Adam S.</searchLink><relatesTo>2</relatesTo><br /><searchLink fieldCode="AR" term="%22Zhang%2C+Yongbin%22">Zhang, Yongbin</searchLink><relatesTo>1</relatesTo><br /><searchLink fieldCode="AR" term="%22Zhang%2C+Lifei%22">Zhang, Lifei</searchLink><relatesTo>1</relatesTo><br /><searchLink fieldCode="AR" term="%22Dong%2C+Lei%22">Dong, Lei</searchLink><relatesTo>1</relatesTo> – Name: TitleSource Label: Source Group: Src Data: <searchLink fieldCode="JN" term="%22Medical+Physics%22">Medical Physics</searchLink>. Aug2012, Vol. 39 Issue 8, p5136-5144. 9p. – Name: Subject Label: Subjects Group: Su Data: <searchLink fieldCode="DE" term="%22Cancer+radiotherapy%22">Cancer radiotherapy</searchLink><br /><searchLink fieldCode="DE" term="%22Head+%26+neck+cancer+treatment%22">Head & neck cancer treatment</searchLink><br /><searchLink fieldCode="DE" term="%22Cancer+tomography%22">Cancer tomography</searchLink><br /><searchLink fieldCode="DE" term="%22Medical+protocols%22">Medical protocols</searchLink><br /><searchLink fieldCode="DE" term="%22Image+registration%22">Image registration</searchLink><br /><searchLink fieldCode="DE" term="%22Gaussian+processes%22">Gaussian processes</searchLink> – Name: Abstract Label: Abstract Group: Ab Data: Purpose: To develop a method for creating variable planning margins around a clinical treatment volume (CTV) and to evaluate its application in head and neck cancer radiotherapy in accounting for locoregional variations of nonrigid setup uncertainties. Methods: Ten computed tomography (CT) images (with a resolution of 0.68 × 0.68 × 2.5 mm3) of a head and neck cancer patient were acquired from the first two weeks of treatment for this study. Five rigid structures (the C2, C5, and caudal C7 vertebrae, mandible, and jugular notch) were used as the landmarks for creating variable local margins. At different CTV locations, local margins were calculated as the weighted average of margins determined at different landmark points from previous studies. The weight was determined by a Gaussian falloff function of the distance between the current location and each landmark point. The CTV delineated on the planning CT image, spanning from the upper portion of the mouth to the lower part of the neck, was expanded to form the planning treatment volume (PTV) with either variable or the conventional constant margins. To evaluate the target coverage, the original planning CTV was deformably mapped to each daily treatment CT using a deformable image registration method. We examined the overlap of the deformed CTV and the rigidly aligned PTV for each margin design strategy and compared the efficacy of the variable margin with the constant margin approach. Results: For the variable margin approach with a baseline C2 margin of 2.5 mm in the left-right, anterior-posterior, and superior-inferior directions, an average of 99.2% of the CTV was within the PTV, and for the approach with a constant 2.5 mm margin, an average of 97.9% of the CTV was within the PTV. With a baseline margin of 2.0 mm, the variable margin approach had an average coverage of 97.8%, similar to that of the constant 2.5 mm margin approach. However, its average nonoverlapped PTV proportion was 32.4%, smaller than that of the constant 2.5 mm margin approach (33.7%). Paired t-tests of computations from the ten treatment fractions showed no significant difference in CTV coverage for the variable margin approach with a baseline of 2.0 mm and the constant 2.5 margin approach (p = 0.054), but the nonoverlapped PTV proportion was significantly smaller for the variable margin approach with a baseline of 2.0 mm than for the constant 2.5 mm margin approach (p < 0.0001). The CTV coverage with the variable margin approach was also significantly higher than with the constant margin approach in the lower neck area, where a larger setup error normally occurs. Conclusions: We implemented a variable margin approach to account for locoregional variations of setup uncertainties for head and neck cancer radiotherapy, and demonstrated the effectiveness of this approach when compared with the conventional global constant margin expansion approach, where the treatment target spreads out to a broad region. As variable margin data become available and more clinical studies are performed, this approach could be applicable to other treatment sites as well. [ABSTRACT FROM AUTHOR] – Name: AbstractSuppliedCopyright Label: Group: Ab Data: <i>Copyright of Medical Physics is the property of Wiley-Blackwell and its content may not be copied or emailed to multiple sites without the copyright holder's express written permission. Additionally, content may not be used with any artificial intelligence tools or machine learning technologies. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract.</i> (Copyright applies to all Abstracts.) |
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| RecordInfo | BibRecord: BibEntity: Identifiers: – Type: doi Value: 10.1118/1.4737891 Languages: – Code: eng Text: English PhysicalDescription: Pagination: PageCount: 9 StartPage: 5136 Subjects: – SubjectFull: Cancer radiotherapy Type: general – SubjectFull: Head & neck cancer treatment Type: general – SubjectFull: Cancer tomography Type: general – SubjectFull: Medical protocols Type: general – SubjectFull: Image registration Type: general – SubjectFull: Gaussian processes Type: general Titles: – TitleFull: Variable planning margin approach to account for locoregional variations in setup uncertainties. Type: main BibRelationships: HasContributorRelationships: – PersonEntity: Name: NameFull: Yang, Jinzhong – PersonEntity: Name: NameFull: Garden, Adam S. – PersonEntity: Name: NameFull: Zhang, Yongbin – PersonEntity: Name: NameFull: Zhang, Lifei – PersonEntity: Name: NameFull: Dong, Lei IsPartOfRelationships: – BibEntity: Dates: – D: 01 M: 08 Text: Aug2012 Type: published Y: 2012 Identifiers: – Type: issn-print Value: 00942405 Numbering: – Type: volume Value: 39 – Type: issue Value: 8 Titles: – TitleFull: Medical Physics Type: main |
| ResultId | 1 |
