Measurement of neutron dose equivalent to proton therapy patients outside of the proton radiation field

Yan, X. L.; Titt, Uwe; Koehler, Andreas; Newhauser, Wayne D.

doi:10.1016/s0168-9002(01)01483-8

Cited by 147 publications

(147 citation statements)

References 5 publications

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“…This is in good agreement with previous H/D determinations made in the presence of a phantom. Specifically, measured H/D values from Yan et al (2002) and simulated H/D values from and Zheng et al (2008) ranged from 1 mSv Gy −1 to 15 mSv Gy −1 , depending on the location and other variables.…”

Section: Discussionmentioning

confidence: 99%

“…For lowdensity shielding materials, such as PMMA, polyethylene and concrete, relatively small ΔE values were observed. In the case of polyethylene, adding boron as a thermal neutron absorber to the material composition did not significantly reduce E because thermal neutrons contributed only a small proportion to H T (Yan et al 2002. When relatively high-density steel was used for the first layer of supplemental shielding, E was reduced considerably more than when PMMA was used for both layers.…”

Section: Local Bulk Shielding Selectionmentioning

confidence: 96%

“…Measurements and simulations of equivalent dose and ambient dose equivalent from stray radiation per therapeutic dose (H/D) for passively scattered proton beams have ranged from <1 mSv Gy −1 to 80 mSv Gy −1 (cf Binns and Hough, 1997, Yan et al 2002, Zheng et al 2007. For a spot-scanning beam of 177 MeV protons, Schneider et al (2002) reported ambient dose equivalent from stray radiation that ranged from 0.9 mSv Gy −1 to 37 mSv Gy −1 , depending on the measurement location in a water phantom.…”

Section: Introductionmentioning

confidence: 99%

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Reducing stray radiation dose to patients receiving passively scattered proton radiotherapy for prostate cancer

et al. 2008

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Proton beam radiotherapy exposes healthy tissue to stray radiation emanating from the treatment unit and secondary radiation produced within the patient. These exposures provide no known benefit and may increase a patient's risk of developing a radiogenic second cancer. The aim of this study was to explore strategies to reduce stray radiation dose to a patient receiving a 76 Gy proton beam treatment for cancer of the prostate. The whole-body effective dose from stray radiation, E, was estimated using detailed Monte Carlo simulations of a passively scattered proton treatment unit and an anthropomorphic phantom. The predicted value of E was 567 mSv, of which 320 mSv was attributed to leakage from the treatment unit; the remainder arose from scattered radiation that originated within the patient. Modest modifications of the treatment unit reduced E by 212 mSv. Surprisingly, E from a modified passive-scattering device was only slightly higher (109 mSv) than from a nozzle with no leakage, e.g., that which may be approached with a spot-scanning technique. These results add to the body of evidence supporting the suitability of passively scattered proton beams for the treatment of prostate cancer, confirm that the effective dose from stray radiation was not excessive, and, importantly, show that it can be substantially reduced by modest enhancements to the treatment unit.

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Section: Discussionmentioning

confidence: 99%

Section: Local Bulk Shielding Selectionmentioning

confidence: 96%

Section: Introductionmentioning

confidence: 99%

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Reducing stray radiation dose to patients receiving passively scattered proton radiotherapy for prostate cancer

et al. 2008

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“…There are also several reports of measurements with detectors such as track etch detectors 14,18 or thermoluminescent detectors 19 that have limited or no response to neutrons with energies greater than 10 MeV. There are a few reports that include neutron spectra measured with a Bonner sphere spectrometer (BSS), 11,20 which can be used to deduce neutron spectra. However, these studies used standard BSSs, which have a very low and nondifferentiating response to highenergy neutrons (>20 MeV).…”

Section: Introductionmentioning

confidence: 99%

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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“…• the energy of the protons, which mainly changes the fluence and shifts the endpoint of the spectrum to the energy of the beam [3][4] • the angle to the proton beam, which changes the shape of the fast neutron spectrum [5][6] [7][8] [9] • the distance to isocentre, which changes not only the fluence but also the shape of the spectrum [10][11] [12] Because of that, one spectrum can only be identified to one treatment. Scarce experimental data coupled to extrapolation via Monte Carlo simulation is currently used to estimate the dose, but this leads to large discrepancies between the simulation and experimental data.…”

Section: A Z X(p N)mentioning

confidence: 99%

Conception of a New Recoil Proton Telescope for Real-Time Neutron Spectrometry in Proton-Therapy

et al. 2018

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Abstract-Neutrons are the main type of secondary particles emitted in proton-therapy. Because of the risk of secondary cancer and other late occurring effects, the neutron dose should be included in the out-of-field dose calculations. A neutron spectrometer has to be used to take into account the energy dependence of the neutron radiological weighting factor. Due to its high dependence on various parameters of the irradiation (beam, accelerator, patient), the neutron spectrum should be measured independently for each treatment.The current reference method for the measurement of the neutron energy, the Bonner Sphere System, consists of several homogeneous polyethylene spheres with increasing diameters equipped with a proportional counter. It provides a highresolution reconstruction of the neutron spectrum but requires a time-consuming work of signal deconvolution. New neutron spectrometers are being developed, but the main experimental limitation remains the high neutron flux in proton therapy treatment rooms. A new model of a real-time neutron spectrometer, based on a Recoil Proton Telescope technology, has been developed at the IPHC. It enables a real-time high-rate reconstruction of the neutron spectrum from the measurement of the recoil proton trajectory and energy. A new fast-readout microelectronic integrated sensor, called FastPixN, has been developed for this specific purpose.A first prototype, able to detect neutrons between 5 and 20 MeV, has already been validated for metrology with the AMANDE facility at Cadarache. The geometry of the new Recoil Proton Telescope has been optimized via extensive Geant4 Monte Carlo simulations. Uncertainty sources have been carefully studied in order to improve simultaneously efficiency and energy resolution, and solutions have been found to suppress the various expected backgrounds. We are currently upgrading the prototype for secondary neutron detection in proton therapy applications.

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Measurement of neutron dose equivalent to proton therapy patients outside of the proton radiation field

Cited by 147 publications

References 5 publications

Reducing stray radiation dose to patients receiving passively scattered proton radiotherapy for prostate cancer

Reducing stray radiation dose to patients receiving passively scattered proton radiotherapy for prostate cancer

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

Conception of a New Recoil Proton Telescope for Real-Time Neutron Spectrometry in Proton-Therapy

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