Measurement of neutron dose equivalent outside and inside of the treatment vault of GRID therapy

Wang, Xudong; Charlton, M. A.; Esquivel, Carlos O.; Eng, Tony Y.; Liu, Ying; Papanikolaou, Nikos

doi:10.1118/1.4816653

Cited by 9 publications

(15 citation statements)

References 24 publications

(34 reference statements)

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“… Measurements of neutron absorbed dose and neutron dose equivalent at proton therapy beam lines were executed. First, measurements on passive beam lines were undertaken by Binns and Hough ( 8 ) and Yan et al ( 9 ) and for active beam lines by Schneider et al ( 10 ). Since then, a large number of neutron dose measurements were reported including several beam lines, in patient measurements, as well as measurements in treatment rooms, including a variety of dosimeters and set-ups including neutron energy spectra measurements.…”

Section: Introductionmentioning

confidence: 99%

The Impact of Neutrons in Clinical Proton Therapy

Schneider¹,

Hälg²

2015

Front. Oncol.

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In proton therapy, high-energy proton beams cause the production of secondary neutrons. This leads to an unwanted dose contribution, which can be considerable for tissues outside of the target volume regarding the long-term health of cancer patients. Due to the high biological effectiveness of neutrons with regard to cancer induction, small neutron doses can be important. Published comparisons of neutron dose measurements and the corresponding estimates of cancer risk between different treatment modalities differ over orders of magnitude. In this report, the controversy about the impact of the neutron dose in proton therapy is critically discussed and viewed in the light of new epidemiological studies. In summary, the impact of neutron dose on cancer risk can be determined correctly only if the dose distributions are carefully measured or computed. It is important to include not only the neutron component into comparisons but also the complete deposition of energy as precisely as possible. Cancer risk comparisons between different radiation qualities, treatment machines, and techniques have to be performed under similar conditions. It seems that in the past, the uncertainty in the models which lead from dose to risk were overestimated when compared with erroneous dose comparisons. Current risk models used with carefully obtained dose distributions predict a second cancer risk reduction for active protons vs. photons and a more or less constant risk of passive protons vs. photons. Those findings are in general agreement with newly obtained epidemiologically results.

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Section: Introductionmentioning

confidence: 99%

The Impact of Neutrons in Clinical Proton Therapy

Schneider¹,

Hälg²

2015

Front. Oncol.

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“…20 Regarding the brass grid block, however, neutron dose and radiation activation are concerns for high energy beams. 21 A unique hybrid collimation system for megavoltage grid therapy was proposed that uses two perpendicular sets of equally spaced rectangular openings, with one set defined by the MLC and the other by Cerrobend bars. While this orthogonal grid pattern results in more efficient delivery, 22 it is still difficult to customize grid patterns.…”

Section: Introductionmentioning

confidence: 99%

Technical Note: Fabricating Cerrobend grids with 3D printing for spatially modulated radiation therapy: A feasibility study

Zhu

Driewer

et al. 2015

Medical Physics

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“…This seems in contrast with Wang et al . 's results,[ 23 ] who showed that the GRID reduced the dose equivalent of thermal neutrons 39.3% (at the IC). The reason for this disagreement could be this point that our calculations were done in the air while their dosimeter was attached to the left buccal side of the RANDO ® phantom.…”

Section: Discussionmentioning

confidence: 99%

“…'s study. [ 23 ] The genus of the GRID is brass (63% copper and 37% zinc) and has a thickness of 7.62 cm. The conical holes of this GRID follow direction of radiation divergence.…”

Section: Methodsmentioning

confidence: 99%

“…Although, by measuring, Wang et al . [ 23 ] showed that in GRID therapy with 18-MV photon beams, neutron dose equivalent received by the patient is on average 35.3% lower conventional radiotherapy (when the same MU and treatment field size are used). So far the effects of GRID on the neutron source strength of LINAC and the distribution of neutron dose on the treatment table have not been studied.…”

Section: Introductionmentioning

confidence: 99%

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Photoneutron dose estimation in GRID therapy using an anthropomorphic phantom: A monte carlo study

et al. 2018

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Background:In the past, GRID therapy was used as a treatment modality for the treatment of bulky and deeply seated tumors with orthovoltage beams. Now and with the introduction of megavoltage beams to radiotherapy, some of the radiotherapy institutes use GRID therapy with megavoltage photons for the palliative treatment of bulky tumors. Since GRID can be a barrier for weakening the photoneutrons produced in the head of medical linear accelerators (LINAC), as well as a secondary source for producing photoneutrons, therefore, in terms of radiation protection, it is important to evaluate the GRID effect on photoneutron dose to the patients.Methods:In this study, using the Monte Carlo code MCNPX, a full model of a LINAC was simulated and verified. The neutron source strength of the LINAC (Q), the distributions of flux (φ), and ambient dose equivalent (H*[10]) of neutrons were calculated on the treatment table in both cases of with/without the GRID. Finally, absorbed dose and dose equivalent of neutrons in some of the tissues/organs of MIRD phantom were computed with/without the GRID.Results:Our results indicate that the GRID increases the production of the photoneutrons in the LINAC head only by 0.3%. The calculations in the MIRD phantom show that neutron dose in the organs/tissues covered by the GRID is on average by 48% lower than conventional radiotherapy. In addition, in the uncovered organs (by the GRID), this amount is reduced to 25%.Conclusion:Based on the findings of this study, in GRID therapy technique compared to conventional radiotherapy, the neutron dose in the tissues/organs of the body is dramatically reduced. Therefore, there will be no concern about the GRID effect on the increase of unwanted neutron dose, and consequently the risk of secondary cancer.

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Measurement of neutron dose equivalent outside and inside of the treatment vault of GRID therapy

Cited by 9 publications

References 24 publications

The Impact of Neutrons in Clinical Proton Therapy

The Impact of Neutrons in Clinical Proton Therapy

Technical Note: Fabricating Cerrobend grids with 3D printing for spatially modulated radiation therapy: A feasibility study

Photoneutron dose estimation in GRID therapy using an anthropomorphic phantom: A monte carlo study

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