title: Experimental Comparison of Knife-Edge and Multi-Parallel Slit Collimators for Prompt Gamma Imaging of Proton Pencil Beams.
abstract: More and more camera concepts are being investigated to try and seize the opportunity of instantaneous range verification of proton therapy treatments offered by prompt gammas emitted along the proton tracks. Focusing on one-dimensional imaging with a passive collimator, the present study experimentally compared in combination with the first, clinically compatible, dedicated camera device the performances of instances of the two main options: a knife-edge slit (KES) and a multi-parallel slit (MPS) design. These two options were experimentally assessed in this specific context as they were previously demonstrated through analytical and numerical studies to allow similar performances in terms of Bragg peak retrieval precision and spatial resolution in a general context. Both collimators were prototyped according to the conclusions of Monte Carlo optimization studies under constraints of equal weight (40 mm tungsten alloy equivalent thickness) and of the specificities of the camera device under consideration (in particular 4 mm segmentation along beam axis and no time-of-flight discrimination, both of which less favorable to the MPS performance than to the KES one). Acquisitions of proton pencil beams of 100, 160, and 230 MeV in a PMMA target revealed that, in order to reach a given level of statistical precision on Bragg peak depth retrieval, the KES collimator requires only half the dose the present MPS collimator needs, making the KES collimator a preferred option for a compact camera device aimed at imaging only the Bragg peak position. On the other hand, the present MPS collimator proves more effective at retrieving the entrance of the beam in the target in the context of an extended camera device aimed at imaging the whole proton track within the patient.
authors.affiliation: Ion Beam Applications SA , Louvain-la-Neuve , Belgium.
authors.forename: Julien
authors.initials: J
authors.lastname: Smeets
authors.affiliation: Ion Beam Applications SA, Louvain-la-Neuve, Belgium; IPNL, Université Lyon 1 and CNRS/IN2P3, Lyon, France; Université Lyon, INSA - Lyon, Université Lyon 1, UJM-Saint Etienne, CNRS, Inserm, Centre Léon Bérard, CREATIS UMR 5220 U1206, Lyon, France.
authors.forename: Frauke
authors.initials: F
authors.lastname: Roellinghoff
authors.affiliation: Ion Beam Applications SA , Louvain-la-Neuve , Belgium.
authors.forename: Guillaume
authors.initials: G
authors.lastname: Janssens
authors.affiliation: Politecnico di Milano, Dipartimento di Elettronica, Informazione e Bioingegneria, Milano, Italy; Istituto Nazionale di Fisica Nucleare, Sezione di Milano, Milano, Italy.
authors.forename: Irene
authors.initials: I
authors.lastname: Perali
authors.affiliation: XGLab SRL , Milano , Italy.
authors.forename: Andrea
authors.initials: A
authors.lastname: Celani
authors.affiliation: Politecnico di Milano, Dipartimento di Elettronica, Informazione e Bioingegneria, Milano, Italy; Istituto Nazionale di Fisica Nucleare, Sezione di Milano, Milano, Italy.
authors.forename: Carlo
authors.initials: C
authors.lastname: Fiorini
authors.affiliation: Université Lyon, INSA - Lyon, Université Lyon 1, UJM-Saint Etienne, CNRS, Inserm, Centre Léon Bérard, CREATIS UMR 5220 U1206 , Lyon , France.
authors.forename: Nicolas
authors.initials: N
authors.lastname: Freud
authors.affiliation: IPNL, Université Lyon 1 and CNRS/IN2P3 , Lyon , France.
authors.forename: Etienne
authors.initials: E
authors.lastname: Testa
authors.affiliation: Ion Beam Applications SA , Louvain-la-Neuve , Belgium.
authors.forename: Damien
authors.initials: D
authors.lastname: Prieels
keywords: prompt gamma imaging; proton therapy; range verification