title: Time-resolved imaging of prompt-gamma rays for proton range verification using a knife-edge slit camera based on digital photon counters.
abstract: Proton range monitoring may facilitate online adaptive proton therapy and improve treatment outcomes. Imaging of proton-induced prompt gamma (PG) rays using a knife-edge slit collimator is currently under investigation as a potential tool for real-time proton range monitoring. A major challenge in collimated PG imaging is the suppression of neutron-induced background counts. In this work, we present an initial performance test of two knife-edge slit camera prototypes based on arrays of digital photon counters (DPCs). PG profiles emitted from a PMMA target upon irradiation with a 160 MeV proton pencil beams (about 6.5 × 10(9) protons delivered in total) were measured using detector modules equipped with four DPC arrays coupled to BGO or LYSO : Ce crystal matrices. The knife-edge slit collimator and detector module were placed at 15 cm and 30 cm from the beam axis, respectively, in all cases. The use of LYSO : Ce enabled time-of-flight (TOF) rejection of background events, by synchronizing the DPC readout electronics with the 106 MHz radiofrequency signal of the cyclotron. The signal-to-background (S/B) ratio of 1.6 obtained with a 1.5 ns TOF window and a 3 MeV-7 MeV energy window was about 3 times higher than that obtained with the same detector module without TOF discrimination and 2 times higher than the S/B ratio obtained with the BGO module. Even 1 mm shifts of the Bragg peak position translated into clear and consistent shifts of the PG profile if TOF discrimination was applied, for a total number of protons as low as about 6.5 × 10(8) and a detector surface of 6.6 cm × 6.6 cm.
authors.affiliation: Delft University of Technology, Faculty of Applied Sciences, Mekelweg 15, 2629 JB Delft, The Netherlands. Laboratório de Instrumentação e Física Experimental de Partículas, Coimbra, Portugal. Heidelberg Ion-Beam Therapy Center, Heidelberg University Clinic, Heidelberg, Germany.
authors.forename: Patricia
authors.initials: P
authors.lastname: Cambraia Lopes
authors.forename: Enrico
authors.initials: E
authors.lastname: Clementel
authors.forename: Paulo
authors.initials: P
authors.lastname: Crespo
authors.forename: Sebastien
authors.initials: S
authors.lastname: Henrotin
authors.forename: Jan
authors.initials: J
authors.lastname: Huizenga
authors.forename: Guillaume
authors.initials: G
authors.lastname: Janssens
authors.forename: Katia
authors.initials: K
authors.lastname: Parodi
authors.forename: Damien
authors.initials: D
authors.lastname: Prieels
authors.forename: Frauke
authors.initials: F
authors.lastname: Roellinghoff
authors.forename: Julien
authors.initials: J
authors.lastname: Smeets
authors.forename: Frederic
authors.initials: F
authors.lastname: Stichelbaut
authors.forename: Dennis R
authors.initials: DR
authors.lastname: Schaart
mesh_terms: D015902:Gamma Cameras; D005720:Gamma Rays; D009502:Neutrons; D017785:Photons; D061766:Proton Therapy / Q000295:instrumentation / Q000379:methods*; D011522:Protons; D011829:Radiation Dosage
chemical_list: D011522:Protons