A scintillator‐based approach to monitor secondary neutron production during proton therapy. Issue 11 (10th October 2016)

• Record Type: Journal Article
• Authors: Clarke, S. D.; Pryser, E.; Wieger, B. M.; Pozzi, S. A.; Haelg, R. A.; Bashkirov, V. A.; Schulte, R. W.
• Is Part Of: Medical physics. Volume 43:Issue 11(2016)
• Page Start: 5915
• Page End: 5924
• Publication Date: 2016-10-10
• Subjects: dosimetry -- Monte Carlo methods -- paediatrics -- patient monitoring -- phantoms -- radiation therapy -- scintillation counters; Therapeutic applications, including brachytherapy -- Scintillation detectors; Radiation therapy -- Measurement of nuclear or x‐radiation -- Tubes for determining the presence, intensity, density or energy of radiation or particles -- Scintigraphy -- the detector being a crystal -- with semiconductor detectors -- Plates or blocks in which tracks of nuclear particles are made visible by after‐treatment, e.g. using photographic emulsion, using mica; proton therapy -- dosimetry -- neutron dose -- Monte Carlo; Neutrons -- Protons -- Neutron radiation effects -- Dosimetry -- Proton therapy -- Scintillation detectors -- Gamma rays -- Neutron spectroscopy -- Tissues -- Position sensitive detectors; Medical physics -- Periodicals; Medical physics; Geneeskunde; Natuurkunde; Toepassingen; Biophysics; Periodicals; Periodicals; Electronic journals; 610.153
• DOI: 10.1118/1.4963813
• Languages: English
• ISSNs: 0094-2405

Abstract

Abstract : Purpose: 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 codemcnpx ‐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. Methods: 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. Themcnpx ‐PoliMi code was used to simulate the secondary neutron field produced during proton irradiation of the same tissue‐equivalent phantom materials. Results: An experiment was performed at the Loma Linda University Medical Center proton therapy research beam line and corresponding models were created using themcnpx ‐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. Conclusions: 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.