VMAT and IMRT plan‐specific correction factors for linac‐based ionization chamber dosimetry.
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| Title: | VMAT and IMRT plan‐specific correction factors for linac‐based ionization chamber dosimetry. |
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| Authors: | Desai, Vimal K.1 (AUTHOR) vkdesai@wisc.edu, Labby, Zacariah E.2 (AUTHOR), Hyun, Megan A.3 (AUTHOR), DeWerd, Larry A.1 (AUTHOR), Culberson, Wesley S.1 (AUTHOR) |
| Source: | Medical Physics. Feb2019, Vol. 46 Issue 2, p913-924. 12p. |
| Subjects: | Volumetric-modulated arc therapy, Correction factors, Ionization chambers, Radiation dosimetry, Intensity modulated radiotherapy |
| Abstract: | Purpose: The determination of absorbed dose to water from external beam radiotherapy using radiation detectors is currently rooted in calibration protocols that do not account for modulations encountered in patient‐specific deliveries. Detector response in composite clinical fields has not been extensively studied due to the time and effort required to determine these corrections on a case‐by‐case basis. To help bridge this gap in knowledge, corrections for the Exradin A1SL scanning chamber were determined in a large number of composite clinical fields using Monte Carlo methods. The chamber‐specific perturbations that contribute the most to the overall correction factor were also determined. Methods: A total of 131 patient deliveries comprised of 834 beams from a Varian C‐arm linear accelerator were converted to EGSnrc Monte Carlo inputs. A validated BEAMnrc 21EX linear accelerator model was used as a particle source throughout the EGSnrc simulations. Composite field dose distributions were compared against a commercial treatment planning system for validation. The simulation geometry consisted of a cylindrically symmetric water‐equivalent phantom with the Exradin A1SL scanning chamber embedded inside. Various chamber perturbation factors were investigated in the egs_chamber user code of EGSnrc and were compared to reference field conditions to determine the plan‐specific correction factor. Results: The simulation results indicated that the Exradin A1SL scanning chamber is suitable to use as an absolute dosimeter within a high‐dose and low‐gradient target region in most nonstandard composite fields; however, there are still individual cases that require larger delivery‐specific corrections. The volume averaging and replacement perturbations showed the largest impact on the overall plan‐specific correction factor for the Exradin A1SL scanning chamber, and both volumetric modulated arc therapy (VMAT) and step‐and‐shoot beams demonstrated similar correction factor magnitudes among the data investigated. Total correction magnitudes greater than 2% were required by 9.1% of step‐and‐shoot beams and 14.5% of VMAT beams. When examining full composite plan deliveries as opposed to individual beams, 0.0% of composite step‐and‐shoot plans and 2.6% of composite VMAT plans required correction magnitudes greater than 2%. Conclusions: The A1SL scanning chamber was found to be suitable to use for absolute dosimetry in high‐dose and low‐gradient dose regions of composite IMRT plans but even if a composite dose distribution is large compared to the detector used, a correction‐free absorbed dose‐to‐water measurement is not guaranteed. [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 |
| FullText | Links: – Type: pdflink Text: Availability: 0 |
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| Header | DbId: egs DbLabel: Engineering Source An: 134577192 AccessLevel: 6 PubType: Academic Journal PubTypeId: academicJournal PreciseRelevancyScore: 0 |
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| Items | – Name: Title Label: Title Group: Ti Data: VMAT and IMRT plan‐specific correction factors for linac‐based ionization chamber dosimetry. – Name: Author Label: Authors Group: Au Data: <searchLink fieldCode="AR" term="%22Desai%2C+Vimal+K%2E%22">Desai, Vimal K.</searchLink><relatesTo>1</relatesTo> (AUTHOR)<i> vkdesai@wisc.edu</i><br /><searchLink fieldCode="AR" term="%22Labby%2C+Zacariah+E%2E%22">Labby, Zacariah E.</searchLink><relatesTo>2</relatesTo> (AUTHOR)<br /><searchLink fieldCode="AR" term="%22Hyun%2C+Megan+A%2E%22">Hyun, Megan A.</searchLink><relatesTo>3</relatesTo> (AUTHOR)<br /><searchLink fieldCode="AR" term="%22DeWerd%2C+Larry+A%2E%22">DeWerd, Larry A.</searchLink><relatesTo>1</relatesTo> (AUTHOR)<br /><searchLink fieldCode="AR" term="%22Culberson%2C+Wesley+S%2E%22">Culberson, Wesley S.</searchLink><relatesTo>1</relatesTo> (AUTHOR) – Name: TitleSource Label: Source Group: Src Data: <searchLink fieldCode="JN" term="%22Medical+Physics%22">Medical Physics</searchLink>. Feb2019, Vol. 46 Issue 2, p913-924. 12p. – Name: Subject Label: Subjects Group: Su Data: <searchLink fieldCode="DE" term="%22Volumetric-modulated+arc+therapy%22">Volumetric-modulated arc therapy</searchLink><br /><searchLink fieldCode="DE" term="%22Correction+factors%22">Correction factors</searchLink><br /><searchLink fieldCode="DE" term="%22Ionization+chambers%22">Ionization chambers</searchLink><br /><searchLink fieldCode="DE" term="%22Radiation+dosimetry%22">Radiation dosimetry</searchLink><br /><searchLink fieldCode="DE" term="%22Intensity+modulated+radiotherapy%22">Intensity modulated radiotherapy</searchLink> – Name: Abstract Label: Abstract Group: Ab Data: Purpose: The determination of absorbed dose to water from external beam radiotherapy using radiation detectors is currently rooted in calibration protocols that do not account for modulations encountered in patient‐specific deliveries. Detector response in composite clinical fields has not been extensively studied due to the time and effort required to determine these corrections on a case‐by‐case basis. To help bridge this gap in knowledge, corrections for the Exradin A1SL scanning chamber were determined in a large number of composite clinical fields using Monte Carlo methods. The chamber‐specific perturbations that contribute the most to the overall correction factor were also determined. Methods: A total of 131 patient deliveries comprised of 834 beams from a Varian C‐arm linear accelerator were converted to EGSnrc Monte Carlo inputs. A validated BEAMnrc 21EX linear accelerator model was used as a particle source throughout the EGSnrc simulations. Composite field dose distributions were compared against a commercial treatment planning system for validation. The simulation geometry consisted of a cylindrically symmetric water‐equivalent phantom with the Exradin A1SL scanning chamber embedded inside. Various chamber perturbation factors were investigated in the egs_chamber user code of EGSnrc and were compared to reference field conditions to determine the plan‐specific correction factor. Results: The simulation results indicated that the Exradin A1SL scanning chamber is suitable to use as an absolute dosimeter within a high‐dose and low‐gradient target region in most nonstandard composite fields; however, there are still individual cases that require larger delivery‐specific corrections. The volume averaging and replacement perturbations showed the largest impact on the overall plan‐specific correction factor for the Exradin A1SL scanning chamber, and both volumetric modulated arc therapy (VMAT) and step‐and‐shoot beams demonstrated similar correction factor magnitudes among the data investigated. Total correction magnitudes greater than 2% were required by 9.1% of step‐and‐shoot beams and 14.5% of VMAT beams. When examining full composite plan deliveries as opposed to individual beams, 0.0% of composite step‐and‐shoot plans and 2.6% of composite VMAT plans required correction magnitudes greater than 2%. Conclusions: The A1SL scanning chamber was found to be suitable to use for absolute dosimetry in high‐dose and low‐gradient dose regions of composite IMRT plans but even if a composite dose distribution is large compared to the detector used, a correction‐free absorbed dose‐to‐water measurement is not guaranteed. [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: 10.1002/mp.13293 Languages: – Code: eng Text: English PhysicalDescription: Pagination: PageCount: 12 StartPage: 913 Subjects: – SubjectFull: Volumetric-modulated arc therapy Type: general – SubjectFull: Correction factors Type: general – SubjectFull: Ionization chambers Type: general – SubjectFull: Radiation dosimetry Type: general – SubjectFull: Intensity modulated radiotherapy Type: general Titles: – TitleFull: VMAT and IMRT plan‐specific correction factors for linac‐based ionization chamber dosimetry. Type: main BibRelationships: HasContributorRelationships: – PersonEntity: Name: NameFull: Desai, Vimal K. – PersonEntity: Name: NameFull: Labby, Zacariah E. – PersonEntity: Name: NameFull: Hyun, Megan A. – PersonEntity: Name: NameFull: DeWerd, Larry A. – PersonEntity: Name: NameFull: Culberson, Wesley S. IsPartOfRelationships: – BibEntity: Dates: – D: 01 M: 02 Text: Feb2019 Type: published Y: 2019 Identifiers: – Type: issn-print Value: 00942405 Numbering: – Type: volume Value: 46 – Type: issue Value: 2 Titles: – TitleFull: Medical Physics Type: main |
| ResultId | 1 |
