Measurements of secondary neutron dose from 15 MV and 18 MV IMRT

Howell, Rebecca M.; Ferenci, Michele; Hertel, Nolan E.; Fullerton, Gary D.; Fox, Timothy; Davis, Lawrence W.

doi:10.1093/rpd/nci041

Cited by 37 publications

(13 citation statements)

References 4 publications

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“…2 In many of these studies, spectral measurements have been used to validate the computational models. [3][4][5][6][7][8] In recent years, as the number of proton centers in the United States and worldwide has grown, so too has the literature on secondary neutrons from proton therapy. However, in the vast majority of this literature, the spectra are based on computational methods rather than measurements.…”

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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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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“…BSS-based instruments have isotropic response, wide energy range and allow, in principle, an accurate determination of the neutron spectrum. As central detectors, the most used are activation gold foils (Thomas et al, 2002;Fernández et al, 2007a) and TLD pairs (Barquero et al, 2005;Howell et al, 2005). TLD pairs and gold foils offer different performances, as briefly summarized below.…”

Section: Introductionmentioning

confidence: 99%

Determination of the neutron spectra around an 18MV medical LINAC with a passive Bonner sphere spectrometer based on gold foils and TLD pairs

Esposito

Bedogni

Lembo

et al. 2008

Radiation Measurements

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“…Several studies have measured the neutron dose equivalent for 15-to 18-MV prostate IMRT treatments based on Varian linacs, yielding consistent values in micro-Sievert per MU: 6-15 uSv/MU (14), 11-24 uSv/MU (15), and 21 uSv/Mu (16). These measurements incorporate the neutron energy spectrum with Varian 2100 linacs and have comparable setup and measurement conditions (specifically, distance from central axis to detector ranged from 10 to 15 cm, and depth in tissue equivalent was an average of 10-15 cm).…”

Section: Methodsmentioning

confidence: 99%