Neutron shielding verification measurements and simulations for a 235-MeV proton therapy center

Newhauser, Wayne D.; Titt, Uwe; Dexheimer, D.T.; Yan, X. L.; Nill, Simeon

doi:10.1016/s0168-9002(01)01400-0

Cited by 37 publications

(32 citation statements)

References 5 publications

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“…This general trend in spectra shape as a function of distance from isocenter was observed in Monte Carlo simulations of neutron spectra at increasing distances from the isocenter. 1,54 It is difficult to compare our data with that reported in the literature because of the inherent differences in beamlines at different proton facilities and in measurement conditions, distance from isocenter, aperture configuration, and similar parameters. Our dose equivalent result (1.6 mSv/Gy) is consistent with measured neutron dose equivalents reported in the literature, which vary from 0.25 to 10 mSv/Gy, 11, 15-17, 19, 20 the higher end of the scale occurring with high proton beam energies measured near the isocenter and more collimating material in the beamline.…”

Section: Discussionmentioning

confidence: 91%

Secondary neutron spectrum from 250‐MeV passively scattered proton therapy: Measurement with an extended‐range Bonner sphere system

Howell

Burgett

2014

Medical Physics

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Purpose: Secondary neutrons are an unavoidable consequence of proton therapy. While the neutron dose is low compared to the primary proton dose, its presence and contribution to the patient dose is nonetheless important. The most detailed information on neutrons includes an evaluation of the neutron spectrum. However, the vast majority of the literature that has reported secondary neutron spectra in proton therapy is based on computational methods rather than measurements. This is largely due to the inherent limitations in the majority of neutron detectors, which are either not suitable for spectral measurements or have limited response at energies greater than 20 MeV. Therefore, the primary objective of the present study was to measure a secondary neutron spectrum from a proton therapy beam using a spectrometer that is sensitive to neutron energies over the entire neutron energy spectrum. Methods: The authors measured the secondary neutron spectrum from a 250-MeV passively scattered proton beam in air at a distance of 100 cm laterally from isocenter using an extended-range Bonner sphere (ERBS) measurement system. Ambient dose equivalent H*(10) was calculated using measured fluence and fluence-to-ambient dose equivalent conversion coefficients. Results: The neutron fluence spectrum had a high-energy direct neutron peak, an evaporation peak, a thermal peak, and an intermediate energy continuum between the thermal and evaporation peaks. The H*(10) was dominated by the neutrons in the evaporation peak because of both their high abundance and the large quality conversion coefficients in that energy interval. The H*(10) 100 cm laterally from isocenter was 1.6 mSv per proton Gy (to isocenter). Approximately 35% of the dose equivalent was from neutrons with energies ≥20 MeV. Conclusions: The authors measured a neutron spectrum for external neutrons generated by a 250-MeV proton beam using an ERBS measurement system that was sensitive to neutrons over the entire energy range being measured, i.e., thermal to 250 MeV. The authors used the neutron fluence spectrum to demonstrate experimentally the contribution of neutrons with different energies to the total dose equivalent and in particular the contribution of high-energy neutrons (≥20 MeV). These are valuable reference data that can be directly compared with Monte Carlo and experimental data in the literature. © 2014 Author(s)

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Section: Discussionmentioning

confidence: 91%

Secondary neutron spectrum from 250‐MeV passively scattered proton therapy: Measurement with an extended‐range Bonner sphere system

Howell

Burgett

2014

Medical Physics

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“…Monte Carlo methods also turn out to be powerful in complex situations where measurements are difficult to achieve. They also have many other applications in proton therapy: verification of shielding design efficiency (Newhauser et al, 2002), assessment of secondary doses received by proton therapy patients (Agosteo et al, 1998;Jiang et al, 2005;Zacharatou Jarlskog and Paganetti 2008) and neutron fluence and ambient dose equivalent calculations (Zheng et al, 2008;Perez-Andujar et al, 2009). It should be noted that each Monte Carlo model must first be carefully validated with experimental data in order to verify the accuracy of results.…”

Section: Introductionmentioning

confidence: 99%

Monte Carlo simulation of a proton therapy beamline for intracranial treatments

et al. 2013

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“…These statistical uncertainties can affect the results, especially at the 1 mSv/year value outside the facility (one main objective, as indicated in the introduction). On the other hand, in the study (Newhauser et al, 2002) the comparison of experimental and calculated data is presented for different locations in the Proton Therapy Center and in almost all cases the simulations overestimate the experimental values, typically by more than a factor of 10, and in some cases more than 100. The simulations in (Newhauser et al, 2002) were performed with the same Monte Carlo code as in this study.…”

Section: Discussionmentioning

confidence: 99%

“…On the other hand, in the study (Newhauser et al, 2002) the comparison of experimental and calculated data is presented for different locations in the Proton Therapy Center and in almost all cases the simulations overestimate the experimental values, typically by more than a factor of 10, and in some cases more than 100. The simulations in (Newhauser et al, 2002) were performed with the same Monte Carlo code as in this study. Unfortunately, the experimental data from the Prague Proton-Therapy-Center are not available yet.…”

Section: Discussionmentioning

confidence: 99%

Shielding calculation for the Proton-Therapy-Center in Prague, Czech Republic

Urban¹,

Kluson²

2012

Radioprotection

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The study of radiation fields around the cyclotron room was carried out for the Proton-Therapy-Center in Prague (Czech Republic). The 230 MeV proton cyclotron will be installed there as well as additional components located along the beampath. The ambient doses were computed by taking into account 3 major sources of secondary radiation (neutron and photon) -the cyclotron, energy degrader and its collimator. The fluxes of neutrons/photons produced by protons were computed using Monte Carlo code MCNPX TM 2.5.0. Energy and angular distributions were computed for various targets and proton beam energies. Different physical models of high-energy proton interactions were studied as well. The annual charge at the cyclotron exit was based on the "patient model" (distribution of treatment type) established for a similar therapy center in Essen (Germany). Calculated data were used as an approximation of the radiation field of the most significant sources of radiation (graphite degrader, tantalum collimator). Fluence-to-dose conversion factors from ICRP-74 were used for the annual dose equivalent evaluation. With these results, the shielding analysis in the Therapy-Center was performed in the context of the current legislation requirements.

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Neutron shielding verification measurements and simulations for a 235-MeV proton therapy center

Cited by 37 publications

References 5 publications

Secondary neutron spectrum from 250‐MeV passively scattered proton therapy: Measurement with an extended‐range Bonner sphere system

Secondary neutron spectrum from 250‐MeV passively scattered proton therapy: Measurement with an extended‐range Bonner sphere system

Monte Carlo simulation of a proton therapy beamline for intracranial treatments

Shielding calculation for the Proton-Therapy-Center in Prague, Czech Republic

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