Monte Carlo simulations for configuring and testing an analytical proton dose-calculation algorithm

Newhauser, Wayne D.; Fontenot, Jonas D.; Zheng, Yuanshui; Polf, Jerimy; Titt, Uwe; Koch, N; Zhang, Xiaodong; Mohan, Radhe

doi:10.1088/0031-9155/52/15/014

Cited by 95 publications

(124 citation statements)

References 40 publications

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“…MC-NPX has been benchmarked with experimental measurements for proton therapy and for other physics applications. [19][20][21][22][23][24][25][26][27] It is important to note that in such codes as MCNPX, the accuracy of the result depends directly on the underlying neutron production cross sections and the nuclear physics models used when measured cross sections are not available. MCNPX uses the LANL extensively evaluated LA150 nuclear cross sections below 150 MeV neutron energy and wellestablished nuclear models above this energy.…”

Section: Iib Monte Carlo Neutron Production Simulationsmentioning

confidence: 99%

Maximum proton kinetic energy and patient‐generated neutron fluence considerations in proton beam arc delivery radiation therapy

et al. 2009

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Several compact proton accelerator systems for use in proton therapy have recently been proposed. Of paramount importance to the development of such an accelerator system is the maximum kinetic energy of protons, immediately prior to entry into the patient, that must be reached by the treatment system. The commonly used value for the maximum kinetic energy required for a medical proton accelerator is 250 MeV, but it has not been demonstrated that this energy is indeed necessary to treat all or most patients eligible for proton therapy. This article quantifies the maximum kinetic energy of protons, immediately prior to entry into the patient, necessary to treat a given percentage of patients with rotational proton therapy, and examines the impact of this energy threshold on the cost and feasibility of a compact, gantry-mounted proton accelerator treatment system. One hundred randomized treatment plans from patients treated with IMRT were analyzed. The maximum radiological pathlength from the surface of the patient to the distal edge of the treatment volume was obtained for 180°continuous arc proton therapy and for 180°split arc proton therapy ͑two 90°arcs͒ using CT# profiles from the Pinnacle™ ͑Philips Medical Systems, Madison, WI͒ treatment planning system. In each case, the maximum kinetic energy of protons, immediately prior to entry into the patient, that would be necessary to treat the patient was calculated using proton range tables for various media. In addition, Monte Carlo simulations were performed to quantify neutron production in a water phantom representing a patient as a function of the maximum proton kinetic energy achievable by a proton treatment system. Protons with a kinetic energy of 240 MeV, immediately prior to entry into the patient, were needed to treat 100% of patients in this study. However, it was shown that 90% of patients could be treated at 198 MeV, and 95% of patients could be treated at 207 MeV. Decreasing the proton kinetic energy from 250 to 200 MeV decreases the total neutron energy fluence produced by stopping a monoenergetic pencil beam in a water phantom by a factor of 2.3. It is possible to significantly lower the requirements on the maximum kinetic energy of a compact proton accelerator if the ability to treat a small percentage of patients with rotational therapy is sacrificed. This decrease in maximum kinetic energy, along with the corresponding decrease in neutron production, could lower the cost and ease the engineering constraints on a compact proton accelerator treatment facility.

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Section: Iib Monte Carlo Neutron Production Simulationsmentioning

confidence: 99%

Maximum proton kinetic energy and patient‐generated neutron fluence considerations in proton beam arc delivery radiation therapy

et al. 2009

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“…The upstream collimator (item G in figure 1), also made of tungsten alloy, was located immediately downstream of the range-shifting plates (162 cm away from the surface of the patient and 186 cm upstream of isocenter). The aperture of this additional collimator had the same shape as the aperture of the final collimator, but its lateral dimensions were reduced to take into account the fact that it was closer to the virtual source (cf Newhauser et al 2007a). The lateral dimensions of the aperture were then expanded by 20% to minimize the effects of collimator-scattered protons on the dose distribution of the therapeutic proton beam (Titt et al 2008).…”

Section: Modeling Of the Nozzle Modificationsmentioning

confidence: 99%

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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“…However, in the vast majority of this literature, the spectra are based on computational methods rather than measurements. 1,[9][10][11][12][13][14] There are a few reports of neutron doseequivalent measurements made in proton therapy centers with either the wide-energy neutron detection instrument (WENDI) or smart WENDI (SWENDI), a type of Rem-meter that is sensitive over an energy range adequate for measuring neutrons from proton therapy. [14][15][16][17] Like standard Remmeters, however, these detectors provide only a single doseequivalent value and do not provide the neutron spectrum.…”

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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Monte Carlo simulations for configuring and testing an analytical proton dose-calculation algorithm

Cited by 95 publications

References 40 publications

Maximum proton kinetic energy and patient‐generated neutron fluence considerations in proton beam arc delivery radiation therapy

Maximum proton kinetic energy and patient‐generated neutron fluence considerations in proton beam arc delivery radiation therapy

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

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