A cost-effective monitoring technique in particle therapy via uncollimated prompt gamma peak integration

Abstract : For the purpose of detecting deviations from the prescribed treatment during particle therapy, the integrals of uncollimated prompt gamma-ray timing distributions are investigated. The intention is to provide information, with a simple and cost-effective setup, independent from monitoring devices of the beamline. Measurements have been performed with 65 MeV protons at a clinical cyclotron. Prompt gamma-rays emitted from the target are identified by means of time-of-flight. The proton range inside the PMMA target has been varied via a modulator wheel. The measured variation of the prompt gamma peak integrals as a function of the modulator position is consistent with simulations. With detectors covering a solid angle of 25 msr (corresponding to a diameter of 3–4 in. at a distance of 50 cm from the beam axis) and 108 incident protons, deviations of a few per cent in the prompt gamma-ray count rate can be detected. For the present configuration, this change in the count rate corresponds to a 3 mm change in the proton range in a PMMA target. Furthermore, simulation studies show that a combination of the signals from multiple detectors may be used to detect a misplacement of the target. A different combination of these signals results in a precise number of the detected prompt gamma rays, which is independent on the actual target position.
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Submitted on : Friday, April 14, 2017 - 9:58:23 AM
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J. Krimmer, G. Angellier, L. Balleyguier, D. Dauvergne, N. Freud, et al.. A cost-effective monitoring technique in particle therapy via uncollimated prompt gamma peak integration. Applied Physics Letters, American Institute of Physics, 2017, 110 (15), pp.154102. ⟨10.1063/1.4980103⟩. ⟨hal-01508408⟩



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