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Purpose: The purpose of this study was to verify acquisition feasibility of a single photon emission computed tomography image using prompt gamma rays for proton boron fusion therapy (PBFT) and to confirm an enhanced therapeutic effect of PBFT by comparison with conventional proton therapy without use of boron., Methods: Monte Carlo simulation was performed to acquire reconstructed image during PBFT. We acquired percentage depth dose (PDD) of the proton beams in a water phantom, energy spectrum of the prompt gamma rays, and tomographic images, including the boron uptake region (BUR; target). The prompt gamma ray image was reconstructed using maximum likelihood expectation maximisation (MLEM) with 64 projection raw data. To verify the reconstructed image, both an image profile and contrast analysis according to the iteration number were conducted. In addition, the physical distance between two BURs in the region of interest of each BUR was measured., Results: The PDD of the proton beam from the water phantom including the BURs shows more efficient than that of conventional proton therapy on tumour region. A 719keV prompt gamma ray peak was clearly observed in the prompt gamma ray energy spectrum. The prompt gamma ray image was reconstructed successfully using 64 projections. Different image profiles including two BURs were acquired from the reconstructed image according to the iteration number., Conclusion: We confirmed successful acquisition of a prompt gamma ray image during PBFT. In addition, the quantitative image analysis results showed relatively good performance for further study., (Copyright © 2016 Associazione Italiana di Fisica Medica. Published by Elsevier Ltd. All rights reserved.)

The use of boron (11B) is recently being investigated to be applied in proton therapy as a proton boron fusion dose enhancement agent. Alpha particles are emitted from the p + 11B → 3α fusion (PBF) reaction analogous to the 10B(n,7Li)α capture (BNC) reaction. If a natural boron content (80% 11B and 20% 10B) is used in proton therapy, the contaminated neutrons, induced by the proton beam traversing a water medium, will react with 10B and the primary protons will react with 11B. Each reaction will emit alpha particles according to its reaction cross section. The dose due to these alpha particles, together with the primary proton beam, can induce tumor cell kill. The purpose of this study is to computationally investigate these synergy effects using the Monte Carlo simulation with the target region located in the water medium. A 79.9 MeV proton beam (proton density: 1.9 × 108 cm−2) with 4 monitor unit was used to irradiate the target consisting of water, 10B, 11B, and natural B. The variation of the dose, the location of the reaction, and the energy distribution of the alpha particles were calculated according to the target material. As a result, we confirmed contributions of both BNC and PBF reactions to emitting alpha particles from proton beam irradiation with natural boron. This synergy effect induced an additional 7.29% enhanced dose by 331 984 alpha particles. This enhanced dose can sufficiently reduce the number of treatment fractions in proton therapy. [ABSTRACT FROM AUTHOR]