title: Compton Camera and Prompt Gamma Ray Timing: Two Methods for In Vivo Range Assessment in Proton Therapy.
abstract: Proton beams are promising means for treating tumors. Such charged particles stop at a defined depth, where the ionization density is maximum. As the dose deposit beyond this distal edge is very low, proton therapy minimizes the damage to normal tissue compared to photon therapy. Nevertheless, inherent range uncertainties cast doubts on the irradiation of tumors close to organs at risk and lead to the application of conservative safety margins. This constrains significantly the potential benefits of protons over photons. In this context, several research groups are developing experimental tools for range verification based on the detection of prompt gammas, a nuclear by-product of the proton irradiation. At OncoRay and Helmholtz-Zentrum Dresden-Rossendorf, detector components have been characterized in realistic radiation environments as a step toward a clinical Compton camera. On the one hand, corresponding experimental methods and results obtained during the ENTERVISION training network are reviewed. On the other hand, a novel method based on timing spectroscopy has been proposed as an alternative to collimated imaging systems. The first tests of the timing method at a clinical proton accelerator are summarized, its applicability in a clinical environment for challenging the current safety margins is assessed, and the factors limiting its precision are discussed.
authors.affiliation: Institute of Radiooncology, Helmholtz-Zentrum Dresden - Rossendorf, Dresden, Germany; OncoRay - National Center for Radiation Research in Oncology, Faculty of Medicine and University Hospital Carl Gustav Carus, Technische Universität Dresden, Dresden, Germany.
authors.forename: Fernando
authors.initials: F
authors.lastname: Hueso-González
authors.affiliation: Institute of Radiation Physics, Helmholtz-Zentrum Dresden - Rossendorf , Dresden , Germany.
authors.forename: Fine
authors.initials: F
authors.lastname: Fiedler
authors.affiliation: OncoRay - National Center for Radiation Research in Oncology, Faculty of Medicine and University Hospital Carl Gustav Carus, Technische Universität Dresden , Dresden , Germany.
authors.forename: Christian
authors.initials: C
authors.lastname: Golnik
authors.affiliation: OncoRay - National Center for Radiation Research in Oncology, Faculty of Medicine and University Hospital Carl Gustav Carus, Technische Universität Dresden , Dresden , Germany.
authors.forename: Thomas
authors.initials: T
authors.lastname: Kormoll
authors.affiliation: OncoRay - National Center for Radiation Research in Oncology, Faculty of Medicine and University Hospital Carl Gustav Carus, Technische Universität Dresden , Dresden , Germany.
authors.forename: Guntram
authors.initials: G
authors.lastname: Pausch
authors.affiliation: OncoRay - National Center for Radiation Research in Oncology, Faculty of Medicine and University Hospital Carl Gustav Carus, Technische Universität Dresden , Dresden , Germany.
authors.forename: Johannes
authors.initials: J
authors.lastname: Petzoldt
authors.affiliation: Institute of Radiation Physics, Helmholtz-Zentrum Dresden - Rossendorf , Dresden , Germany.
authors.forename: Katja E
authors.initials: KE
authors.lastname: Römer
authors.affiliation: Institute of Radiooncology, Helmholtz-Zentrum Dresden - Rossendorf, Dresden, Germany; OncoRay - National Center for Radiation Research in Oncology, Faculty of Medicine and University Hospital Carl Gustav Carus, Technische Universität Dresden, Dresden, Germany; German Cancer Consortium (DKTK), German Cancer Research Center (DKFZ), Heidelberg, Germany.
authors.forename: Wolfgang
authors.initials: W
authors.lastname: Enghardt
keywords: Compton imaging; block detector; in vivo dosimetry; prompt gamma ray timing; proton therapy; range verification; scintillation