A scintillator-based approach to monitor secondary neutron production during proton therapy

Journal Article · Mon Oct 10 00:00:00 EDT 2016 · Medical Physics

DOI:https://doi.org/10.1118/1.4963813· OSTI ID:1366700

Clarke, S. D. ^[1]; Pryser, E. ^[2]; Wieger, B. M. ^[2]; Pozzi, S. A. ^[2]; Haelg, R. A. ^[3]; Bashkirov, V. A. ^[4]; Schulte, R. W. ^[4]

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1. Univ. of Michigan, Ann Arbor, MI (United States); Department of Nuclear Engineering and Radiological Sciences, University of Michigan
2. Univ. of Michigan, Ann Arbor, MI (United States)
3. Paul Scherrer Inst. (PSI), Villigen (Switzerland)
4. Loma Linda Univ., Loma Linda, CA (United States)

Here, the primary objective of this work is to measure the secondary neutron field produced by an uncollimated proton pencil beam impinging on different tissue-equivalent phantom materials using organic scintillation detectors. Additionally, the Monte Carlo code mcnpx-PoliMi was used to simulate the detector response for comparison to the measured data. Comparison of the measured and simulated data will validate this approach for monitoring secondary neutron dose during proton therapy. Proton beams of 155- and 200-MeV were used to irradiate a variety of phantom materials and secondary particles were detected using organic liquid scintillators. These detectors are sensitive to fast neutrons and gamma rays: pulse shape discrimination was used to classify each detected pulse as either a neutron or a gamma ray. The mcnpx-PoliMi code was used to simulate the secondary neutron field produced during proton irradiation of the same tissue-equivalent phantom materials. As a result, an experiment was performed at the Loma Linda University Medical Center proton therapy research beam line and corresponding models were created using the mcnpx-PoliMi code. The authors’ analysis showed agreement between the simulations and the measurements. The simulated detector response can be used to validate the simulations of neutron and gamma doses on a particular beam line with or without a phantom. In conclusion, the authors have demonstrated a method of monitoring the neutron component of the secondary radiation field produced by therapeutic protons. The method relies on direct detection of secondary neutrons and gamma rays using organic scintillation detectors. These detectors are sensitive over the full range of biologically relevant neutron energies above 0.5 MeV and allow effective discrimination between neutron and photon dose. Because the detector system is portable, the described system could be used in the future to evaluate secondary neutron and gamma doses on various clinical beam lines for commissioning and prospective data collection in pediatric patients treated with proton therapy.

• Research Organization: Univ. of Michigan, Ann Arbor, MI (United States)
• Sponsoring Organization: USDOE National Nuclear Security Administration (NNSA), Office of Nonproliferation and Verification Research and Development (NA-22)
• Grant/Contract Number: NA0002534
• OSTI ID: 1366700
• Journal Information: Medical Physics, Journal Name: Medical Physics Journal Issue: 11 Vol. 43; ISSN 0094-2405
• Publisher: American Association of Physicists in Medicine
• Country of Publication: United States
• Language: English

Related Subjects

73 NUCLEAR PHYSICS AND RADIATION PHYSICS
Monte Carlo
dosimetry
neutron dose
proton therapy