title: First test of the prompt gamma ray timing method with heterogeneous targets at a clinical proton therapy facility.
abstract: Ion beam therapy promises enhanced tumour coverage compared to conventional radiotherapy, but particle range uncertainties significantly blunt the achievable precision. Experimental tools for range verification in real-time are not yet available in clinical routine. The prompt gamma ray timing method has been recently proposed as an alternative to collimated imaging systems. The detection times of prompt gamma rays encode essential information about the depth-dose profile thanks to the measurable transit time of ions through matter. In a collaboration between OncoRay, Helmholtz-Zentrum Dresden-Rossendorf and IBA, the first test at a clinical proton accelerator (Westdeutsches Protonentherapiezentrum Essen, Germany) with several detectors and phantoms is performed. The robustness of the method against background and stability of the beam bunch time profile is explored, and the bunch time spread is characterized for different proton energies. For a beam spot with a hundred million protons and a single detector, range differences of 5 mm in defined heterogeneous targets are identified by numerical comparison of the spectrum shape. For higher statistics, range shifts down to 2 mm are detectable. A proton bunch monitor, higher detector throughput and quantitative range retrieval are the upcoming steps towards a clinically applicable prototype. In conclusion, the experimental results highlight the prospects of this straightforward verification method at a clinical pencil beam and settle this novel approach as a promising alternative in the field of in vivo dosimetry.
authors.affiliation: OncoRay - National Center for Radiation Research in Oncology, Faculty of Medicine and University Hospital Carl Gustav Carus, Technische Universität Dresden, Fetscherstr. 74, PF 41, 01307 Dresden, Germany. Helmholtz-Zentrum Dresden - Rossendorf, Institute of Radiooncology, Bautzner Landstr. 400, 01328 Dresden, Germany.
authors.forename: Fernando
authors.initials: F
authors.lastname: Hueso-González
authors.forename: Wolfgang
authors.initials: W
authors.lastname: Enghardt
authors.forename: Fine
authors.initials: F
authors.lastname: Fiedler
authors.forename: Christian
authors.initials: C
authors.lastname: Golnik
authors.forename: Guillaume
authors.initials: G
authors.lastname: Janssens
authors.forename: Johannes
authors.initials: J
authors.lastname: Petzoldt
authors.forename: Damien
authors.initials: D
authors.lastname: Prieels
authors.forename: Marlen
authors.initials: M
authors.lastname: Priegnitz
authors.forename: Katja E
authors.initials: KE
authors.lastname: Römer
authors.forename: Julien
authors.initials: J
authors.lastname: Smeets
authors.forename: François
authors.initials: F
authors.lastname: Vander Stappen
authors.forename: Andreas
authors.initials: A
authors.lastname: Wagner
authors.forename: Guntram
authors.initials: G
authors.lastname: Pausch
mesh_terms: D005720:Gamma Rays; D061766:Proton Therapy / Q000379:methods*; D011834:Radiation Monitoring / Q000379:methods*