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Measured Neutron Spectra and Dose Equivalents From a Mevion Single-Room, Passively Scattered Proton System Used for Craniospinal Irradiation.

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Title: Measured Neutron Spectra and Dose Equivalents From a Mevion Single-Room, Passively Scattered Proton System Used for Craniospinal Irradiation.
Authors: Howell, Rebecca M.1 rhowell@mdanderson.org, Burgett, Eric A.2, Isaacs, Daniel2, Price Hedrick, Samantha G.3, Reilly, Michael P.3, Rankine, Leith J.3, Grantham, Kevin K.3, Perkins, Stephanie3, Klein, Eric E.3
Source: International Journal of Radiation Oncology, Biology, Physics. May2016, Vol. 95 Issue 1, p249-257. 9p.
Subjects: Proton therapy, Radiation doses, Scattering (Physics), Neutrons spectra, Separation (Technology)
Abstract: Purpose: To measure, in the setting of typical passively scattered proton craniospinal irradiation (CSI) treatment, the secondary neutron spectra, and use these spectra to calculate dose equivalents for both internal and external neutrons delivered via a Mevion single-room compact proton system.Methods and Materials: Secondary neutron spectra were measured using extended-range Bonner spheres for whole brain, upper spine, and lower spine proton fields. The detector used can discriminate neutrons over the entire range of the energy spectrum encountered in proton therapy. To separately assess internally and externally generated neutrons, each of the fields was delivered with and without a phantom. Average neutron energy, total neutron fluence, and ambient dose equivalent [H* (10)] were calculated for each spectrum. Neutron dose equivalents as a function of depth were estimated by applying published neutron depth-dose data to in-air H* (10) values.Results: For CSI fields, neutron spectra were similar, with a high-energy direct neutron peak, an evaporation peak, a thermal peak, and an intermediate continuum between the evaporation and thermal peaks. Neutrons in the evaporation peak made the largest contribution to dose equivalent. Internal neutrons had a very low to negligible contribution to dose equivalent compared with external neutrons, largely attributed to the measurement location being far outside the primary proton beam. Average energies ranged from 8.6 to 14.5 MeV, whereas fluences ranged from 6.91 × 10(6) to 1.04 × 10(7) n/cm(2)/Gy, and H* (10) ranged from 2.27 to 3.92 mSv/Gy.Conclusions: For CSI treatments delivered with a Mevion single-gantry proton therapy system, we found measured neutron dose was consistent with dose equivalents reported for CSI with other proton beamlines. [ABSTRACT FROM AUTHOR]
Copyright of International Journal of Radiation Oncology, Biology, Physics is the property of Pergamon Press - An Imprint of Elsevier Science 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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  Data: Measured Neutron Spectra and Dose Equivalents From a Mevion Single-Room, Passively Scattered Proton System Used for Craniospinal Irradiation.
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  Data: <searchLink fieldCode="AR" term="%22Howell%2C+Rebecca+M%2E%22">Howell, Rebecca M.</searchLink><relatesTo>1</relatesTo><i> rhowell@mdanderson.org</i><br /><searchLink fieldCode="AR" term="%22Burgett%2C+Eric+A%2E%22">Burgett, Eric A.</searchLink><relatesTo>2</relatesTo><br /><searchLink fieldCode="AR" term="%22Isaacs%2C+Daniel%22">Isaacs, Daniel</searchLink><relatesTo>2</relatesTo><br /><searchLink fieldCode="AR" term="%22Price+Hedrick%2C+Samantha+G%2E%22">Price Hedrick, Samantha G.</searchLink><relatesTo>3</relatesTo><br /><searchLink fieldCode="AR" term="%22Reilly%2C+Michael+P%2E%22">Reilly, Michael P.</searchLink><relatesTo>3</relatesTo><br /><searchLink fieldCode="AR" term="%22Rankine%2C+Leith+J%2E%22">Rankine, Leith J.</searchLink><relatesTo>3</relatesTo><br /><searchLink fieldCode="AR" term="%22Grantham%2C+Kevin+K%2E%22">Grantham, Kevin K.</searchLink><relatesTo>3</relatesTo><br /><searchLink fieldCode="AR" term="%22Perkins%2C+Stephanie%22">Perkins, Stephanie</searchLink><relatesTo>3</relatesTo><br /><searchLink fieldCode="AR" term="%22Klein%2C+Eric+E%2E%22">Klein, Eric E.</searchLink><relatesTo>3</relatesTo>
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  Data: <searchLink fieldCode="JN" term="%22International+Journal+of+Radiation+Oncology%2C+Biology%2C+Physics%22">International Journal of Radiation Oncology, Biology, Physics</searchLink>. May2016, Vol. 95 Issue 1, p249-257. 9p.
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  Data: <searchLink fieldCode="DE" term="%22Proton+therapy%22">Proton therapy</searchLink><br /><searchLink fieldCode="DE" term="%22Radiation+doses%22">Radiation doses</searchLink><br /><searchLink fieldCode="DE" term="%22Scattering+%28Physics%29%22">Scattering (Physics)</searchLink><br /><searchLink fieldCode="DE" term="%22Neutrons+spectra%22">Neutrons spectra</searchLink><br /><searchLink fieldCode="DE" term="%22Separation+%28Technology%29%22">Separation (Technology)</searchLink>
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  Data: <bold>Purpose: </bold>To measure, in the setting of typical passively scattered proton craniospinal irradiation (CSI) treatment, the secondary neutron spectra, and use these spectra to calculate dose equivalents for both internal and external neutrons delivered via a Mevion single-room compact proton system.<bold>Methods and Materials: </bold>Secondary neutron spectra were measured using extended-range Bonner spheres for whole brain, upper spine, and lower spine proton fields. The detector used can discriminate neutrons over the entire range of the energy spectrum encountered in proton therapy. To separately assess internally and externally generated neutrons, each of the fields was delivered with and without a phantom. Average neutron energy, total neutron fluence, and ambient dose equivalent [H* (10)] were calculated for each spectrum. Neutron dose equivalents as a function of depth were estimated by applying published neutron depth-dose data to in-air H* (10) values.<bold>Results: </bold>For CSI fields, neutron spectra were similar, with a high-energy direct neutron peak, an evaporation peak, a thermal peak, and an intermediate continuum between the evaporation and thermal peaks. Neutrons in the evaporation peak made the largest contribution to dose equivalent. Internal neutrons had a very low to negligible contribution to dose equivalent compared with external neutrons, largely attributed to the measurement location being far outside the primary proton beam. Average energies ranged from 8.6 to 14.5 MeV, whereas fluences ranged from 6.91 × 10(6) to 1.04 × 10(7) n/cm(2)/Gy, and H* (10) ranged from 2.27 to 3.92 mSv/Gy.<bold>Conclusions: </bold>For CSI treatments delivered with a Mevion single-gantry proton therapy system, we found measured neutron dose was consistent with dose equivalents reported for CSI with other proton beamlines. [ABSTRACT FROM AUTHOR]
– Name: AbstractSuppliedCopyright
  Label:
  Group: Ab
  Data: <i>Copyright of International Journal of Radiation Oncology, Biology, Physics is the property of Pergamon Press - An Imprint of Elsevier Science 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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