title: In-beam PET at clinical proton beams with pile-up rejection.
abstract: Positron emission tomography (PET) is a means of imaging the β+-activity produced by the radiation field in ion beam therapy and therefore for treatment verification. Prompt γ-rays that are emitted during beam application challenge the detectors and electronics of PET systems, since those are designed for low and medium count rates. Typical PET detectors operated according to a modified Anger principle suffer from multiple events at high rates. Therefore, in-beam PET systems using such detectors rely on a synchronization of beam status and measurement to reject deteriorated data. In this work, a method for pile-up rejection is applied to conventional Anger logic block detectors. It allows for an in-beam data acquisition without further synchronization. Though cyclotrons produce a continuous wave beam, the radiation field shaping technique introduces breaks in the application. Time regimes mimicking synchrotrons as well as cyclotron based ones using double-scattering or pencil beam scanning field shaping at dose rates of 0.5, 1.0 and 2.0Gy/min were investigated. Two types of inhomogeneous phantoms were imaged. The first one simulates cavity structures, the other one mimics a static lung irradiation. It could be shown that, depending on the dose rate and the beam time structure, in-beam measurement including a few seconds decay time only, yield images which revealed all inhomogeneities in the phantoms. This technique can be the basis for the development of an in-beam PET system with traditional detectors and off-the-shelf electronics.
authors.affiliation: Helmholtz-Zentrum Dresden-Rossendorf, Institute of Radiation Physics, Bautzner Landstraße 400, 01328, Germany. Electronic address: s.helmbrecht@hzdr.de.
authors.forename: Stephan
authors.initials: S
authors.lastname: Helmbrecht
authors.affiliation: Helmholtz-Zentrum Dresden-Rossendorf, Institute of Radiation Physics, Bautzner Landstraße 400, 01328, Germany; OncoRay - National Center for Radiation Research in Oncology, Faculty of Medicine and University Hospital Carl Gustav Carus, Technische Universität Dresden, Helmholtz-Zentrum Dresden-Rossendorf, Germany; Helmholtz-Zentrum Dresden-Rossendorf, Institute of Radiooncology, Bautzner Landstraße 400, 01328 Dresden, Germany; German Cancer Consortium (DKTK), Dresden, and German Cancer Research Center (DKFZ), Heidelberg, Germany. Electronic address: Wolfgang.Enghardt@OncoRay.de.
authors.forename: Wolfgang
authors.initials: W
authors.lastname: Enghardt
authors.affiliation: Helmholtz-Zentrum Dresden-Rossendorf, Institute of Radiation Physics, Bautzner Landstraße 400, 01328, Germany. Electronic address: f.fiedler@hzdr.de.
authors.forename: Fine
authors.initials: F
authors.lastname: Fiedler
authors.affiliation: Helmholtz-Zentrum Dresden-Rossendorf, Institute of Radiation Physics, Bautzner Landstraße 400, 01328, Germany. Electronic address: m.iltzsche@hzdr.de.
authors.forename: Marc
authors.initials: M
authors.lastname: Iltzsche
authors.affiliation: OncoRay - National Center for Radiation Research in Oncology, Faculty of Medicine and University Hospital Carl Gustav Carus, Technische Universität Dresden, Helmholtz-Zentrum Dresden-Rossendorf, Germany. Electronic address: Guntram.Pausch@OncoRay.de.
authors.forename: Guntram
authors.initials: G
authors.lastname: Pausch
authors.affiliation: CAEN S.p.A., Viareggio, Italy. Electronic address: c.tintori@caen.it.
authors.forename: Carlo
authors.initials: C
authors.lastname: Tintori
authors.affiliation: OncoRay - National Center for Radiation Research in Oncology, Faculty of Medicine and University Hospital Carl Gustav Carus, Technische Universität Dresden, Helmholtz-Zentrum Dresden-Rossendorf, Germany; now with Institute of Nuclear and Particle Physics, AG Radiation Physics, Technische Universität Dresden, Dresden, Germany. Electronic address: kormoll@asp.tu-dresden.de.
authors.forename: Thomas
authors.initials: T
authors.lastname: Kormoll
mesh_terms: D002138:Calibration; D006801:Humans; D019047:Phantoms, Imaging; D049268:Positron-Emission Tomography / Q000295:instrumentation* / Q000379:methods*; D011522:Protons; D017356:Synchrotrons
chemical_list: D011522:Protons
keywords: In-beam-PET; Ionenstrahltherapie; Pile up; Positron emission tomography; Positronen-Emissions-Tomographie; Protonentherapie; in-beam PET; ion beam therapy; pile up; proton therapy