title: Range assessment in particle therapy based on prompt γ-ray timing measurements.
abstract: Proton and ion beams open up new vistas for the curative treatment of tumors, but adequate technologies for monitoring the compliance of dose delivery with treatment plans in real time are still missing. Range assessment, meaning the monitoring of therapy-particle ranges in tissue during dose delivery (treatment), is a continuous challenge considered a key for tapping the full potential of particle therapies. In this context the paper introduces an unconventional concept of range assessment by prompt-gamma timing (PGT), which is based on an elementary physical effect not considered so far: therapy particles penetrating tissue move very fast, but still need a finite transit time--about 1-2 ns in case of protons with a 5-20 cm range--from entering the patient's body until stopping in the target volume. The transit time increases with the particle range. This causes measurable effects in PGT spectra, usable for range verification. The concept was verified by proton irradiation experiments at the AGOR cyclotron, KVI-CART, University of Groningen. Based on the presented kinematical relations, we describe model calculations that very precisely reproduce the experimental results. As the clinical treatment conditions entail measurement constraints (e.g. limited treatment time), we propose a setup, based on clinical irradiation conditions, capable of determining proton range deviations within a few seconds of irradiation, thus allowing for a fast safety survey. Range variations of 2 mm are expected to be clearly detectable.
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, Fetscherstr. 74, PF 41, 01307 Dresden, Germany.
authors.forename: Christian
authors.initials: C
authors.lastname: Golnik
authors.forename: Fernando
authors.initials: F
authors.lastname: Hueso-González
authors.forename: Andreas
authors.initials: A
authors.lastname: Müller
authors.forename: Peter
authors.initials: P
authors.lastname: Dendooven
authors.forename: Wolfgang
authors.initials: W
authors.lastname: Enghardt
authors.forename: Fine
authors.initials: F
authors.lastname: Fiedler
authors.forename: Thomas
authors.initials: T
authors.lastname: Kormoll
authors.forename: Katja
authors.initials: K
authors.lastname: Roemer
authors.forename: Johannes
authors.initials: J
authors.lastname: Petzoldt
authors.forename: Andreas
authors.initials: A
authors.lastname: Wagner
authors.forename: Guntram
authors.initials: G
authors.lastname: Pausch
mesh_terms: D000465:Algorithms; D005720:Gamma Rays; D006801:Humans; D061766:Proton Therapy / Q000379:methods*; D011829:Radiation Dosage; D011522:Protons
chemical_list: D011522:Protons