Systematic out-of-field secondary neutron spectrometry and dosimetry in pencil beam scanning proton therapy.
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| Title: | Systematic out-of-field secondary neutron spectrometry and dosimetry in pencil beam scanning proton therapy. |
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| Authors: | Trinkl, Sebastian1,2 sebastian.trinkl@gmx.net, Mares, Vladimir1, Englbrecht, Franz Siegfried3, Wilkens, Jan Jakob2,4, Wielunski, Marek1, Parodi, Katia3, Rühm, Werner1, Hillbrand, Martin5 |
| Source: | Medical Physics. May2017, Vol. 44 Issue 5, p1912-1920. 9p. |
| Subjects: | Neutron spectrometers, Radiation dosimetry, Bonner sphere spectrometers, Radiation doses, Proton beams |
| Abstract: | Background and purpose Systematic investigation of the energy and angular dependence of secondary neutron fluence energy distributions and ambient dose equivalents values (H*(10)) inside a pencil beam scanning proton therapy treatment room using a gantry. Materials and methods Neutron fluence energy distributions were measured with an extended-range Bonner sphere spectrometer featuring ³He proportional counters, at four positions at 0°, 45°, 90°, and 135° with respect to beam direction and at a distance of 2 m from the isocenter. The energy distribution of secondary neutrons was investigated for initial proton beam energies of 75 MeV, 140 MeV, and 200 MeV, respectively, using a 2D scanned irradiation field of 11 × 11 cm² delivered to a 30 × 30 × 30 cm³ PMMA phantom. Additional measurements were performed at a proton energy of 118 MeV including a 5 cm range-shifter ( PMMA), yielding a Bragg peak position similar to that of 75 MeV protons. Results Ambient dose equivalent values from 0.3 μSv/Gy (75 MeV; 90°) to 24 μSv/Gy (200 MeV; 0°) were measured inside the treatment room at a distance of 2 m from the isocenter. H*(10) values were lower (by factors of up to 7.2 (at 45°)) at 75 MeV compared to those at 118 MeV with the 5 cm range-shifter. At 0° and 45°, an evaporation peak was found in the measured neutron fluence energy distributions, at neutron energies around MeV, which contributes about 50% to total H*(10) values, for all investigated proton beam energies. Conclusions This study showed a pronounced increase of secondary neutron H*(10) values inside the proton treatment room with increasing proton energy without beam modifiers. For example, in beam direction this increase was about a factor of 50 when protons of 75 MeV and 200 MeV were compared. The existence of a peak of secondary neutrons in the MeV region was demonstrated in beam direction (0°). This peak is due to evaporation neutrons produced in the existing surrounding materials such as those used for the gantry. Therefore, any simulation of the secondary neutrons within a proton treatment room must take these materials into account. In addition, the results obtained here show that the use of a range-shifter increases the production of secondary neutrons inside the treatment room. Using a range-shifter, the higher neutron doses observed mainly result from the higher incident proton energy (118 MeV instead of 75 MeV when no range-shifter was used), due to higher neutron production cross-sections. [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.) | |
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| Header | DbId: egs DbLabel: Engineering Source An: 122988690 AccessLevel: 6 PubType: Academic Journal PubTypeId: academicJournal PreciseRelevancyScore: 0 |
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| Items | – Name: Title Label: Title Group: Ti Data: Systematic out-of-field secondary neutron spectrometry and dosimetry in pencil beam scanning proton therapy. – Name: Author Label: Authors Group: Au Data: <searchLink fieldCode="AR" term="%22Trinkl%2C+Sebastian%22">Trinkl, Sebastian</searchLink><relatesTo>1,2</relatesTo><i> sebastian.trinkl@gmx.net</i><br /><searchLink fieldCode="AR" term="%22Mares%2C+Vladimir%22">Mares, Vladimir</searchLink><relatesTo>1</relatesTo><br /><searchLink fieldCode="AR" term="%22Englbrecht%2C+Franz+Siegfried%22">Englbrecht, Franz Siegfried</searchLink><relatesTo>3</relatesTo><br /><searchLink fieldCode="AR" term="%22Wilkens%2C+Jan+Jakob%22">Wilkens, Jan Jakob</searchLink><relatesTo>2,4</relatesTo><br /><searchLink fieldCode="AR" term="%22Wielunski%2C+Marek%22">Wielunski, Marek</searchLink><relatesTo>1</relatesTo><br /><searchLink fieldCode="AR" term="%22Parodi%2C+Katia%22">Parodi, Katia</searchLink><relatesTo>3</relatesTo><br /><searchLink fieldCode="AR" term="%22Rühm%2C+Werner%22">Rühm, Werner</searchLink><relatesTo>1</relatesTo><br /><searchLink fieldCode="AR" term="%22Hillbrand%2C+Martin%22">Hillbrand, Martin</searchLink><relatesTo>5</relatesTo> – Name: TitleSource Label: Source Group: Src Data: <searchLink fieldCode="JN" term="%22Medical+Physics%22">Medical Physics</searchLink>. May2017, Vol. 44 Issue 5, p1912-1920. 9p. – Name: Subject Label: Subjects Group: Su Data: <searchLink fieldCode="DE" term="%22Neutron+spectrometers%22">Neutron spectrometers</searchLink><br /><searchLink fieldCode="DE" term="%22Radiation+dosimetry%22">Radiation dosimetry</searchLink><br /><searchLink fieldCode="DE" term="%22Bonner+sphere+spectrometers%22">Bonner sphere spectrometers</searchLink><br /><searchLink fieldCode="DE" term="%22Radiation+doses%22">Radiation doses</searchLink><br /><searchLink fieldCode="DE" term="%22Proton+beams%22">Proton beams</searchLink> – Name: Abstract Label: Abstract Group: Ab Data: Background and purpose Systematic investigation of the energy and angular dependence of secondary neutron fluence energy distributions and ambient dose equivalents values (H*(10)) inside a pencil beam scanning proton therapy treatment room using a gantry. Materials and methods Neutron fluence energy distributions were measured with an extended-range Bonner sphere spectrometer featuring ³He proportional counters, at four positions at 0°, 45°, 90°, and 135° with respect to beam direction and at a distance of 2 m from the isocenter. The energy distribution of secondary neutrons was investigated for initial proton beam energies of 75 MeV, 140 MeV, and 200 MeV, respectively, using a 2D scanned irradiation field of 11 × 11 cm² delivered to a 30 × 30 × 30 cm³ PMMA phantom. Additional measurements were performed at a proton energy of 118 MeV including a 5 cm range-shifter ( PMMA), yielding a Bragg peak position similar to that of 75 MeV protons. Results Ambient dose equivalent values from 0.3 μSv/Gy (75 MeV; 90°) to 24 μSv/Gy (200 MeV; 0°) were measured inside the treatment room at a distance of 2 m from the isocenter. H*(10) values were lower (by factors of up to 7.2 (at 45°)) at 75 MeV compared to those at 118 MeV with the 5 cm range-shifter. At 0° and 45°, an evaporation peak was found in the measured neutron fluence energy distributions, at neutron energies around MeV, which contributes about 50% to total H*(10) values, for all investigated proton beam energies. Conclusions This study showed a pronounced increase of secondary neutron H*(10) values inside the proton treatment room with increasing proton energy without beam modifiers. For example, in beam direction this increase was about a factor of 50 when protons of 75 MeV and 200 MeV were compared. The existence of a peak of secondary neutrons in the MeV region was demonstrated in beam direction (0°). This peak is due to evaporation neutrons produced in the existing surrounding materials such as those used for the gantry. Therefore, any simulation of the secondary neutrons within a proton treatment room must take these materials into account. In addition, the results obtained here show that the use of a range-shifter increases the production of secondary neutrons inside the treatment room. Using a range-shifter, the higher neutron doses observed mainly result from the higher incident proton energy (118 MeV instead of 75 MeV when no range-shifter was used), due to higher neutron production cross-sections. [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.12206 Languages: – Code: eng Text: English PhysicalDescription: Pagination: PageCount: 9 StartPage: 1912 Subjects: – SubjectFull: Neutron spectrometers Type: general – SubjectFull: Radiation dosimetry Type: general – SubjectFull: Bonner sphere spectrometers Type: general – SubjectFull: Radiation doses Type: general – SubjectFull: Proton beams Type: general Titles: – TitleFull: Systematic out-of-field secondary neutron spectrometry and dosimetry in pencil beam scanning proton therapy. Type: main BibRelationships: HasContributorRelationships: – PersonEntity: Name: NameFull: Trinkl, Sebastian – PersonEntity: Name: NameFull: Mares, Vladimir – PersonEntity: Name: NameFull: Englbrecht, Franz Siegfried – PersonEntity: Name: NameFull: Wilkens, Jan Jakob – PersonEntity: Name: NameFull: Wielunski, Marek – PersonEntity: Name: NameFull: Parodi, Katia – PersonEntity: Name: NameFull: Rühm, Werner – PersonEntity: Name: NameFull: Hillbrand, Martin IsPartOfRelationships: – BibEntity: Dates: – D: 01 M: 05 Text: May2017 Type: published Y: 2017 Identifiers: – Type: issn-print Value: 00942405 Numbering: – Type: volume Value: 44 – Type: issue Value: 5 Titles: – TitleFull: Medical Physics Type: main |
| ResultId | 1 |
