title: Performance of MACACO Compton telescope for ion-beam therapy monitoring: first test with proton beams.
abstract: In order to exploit the advantages of ion-beam therapy in a clinical setting, delivery verification techniques are necessary to detect deviations from the planned treatment. Efforts are currently oriented towards the development of devices for real-time range monitoring. Among the different detector concepts proposed, Compton cameras are employed to detect prompt gammas and represent a valid candidate for real-time range verification. We present the first on-beam test of MACACO, a Compton telescope (multi-layer Compton camera) based on lanthanum bromide crystals and silicon photo-multipliers. The Compton telescope was first characterized through measurements and Monte Carlo simulations. The detector linearity was measured employing (22)Na and Am-Be sources, obtaining about 10% deviation from linearity at 3.44 MeV. A spectral image reconstruction algorithm was tested on synthetic data. Point-like sources emitting gamma rays with energy between 2 and 7 MeV were reconstructed with 3-5 mm resolution. The two-layer Compton telescope was employed to measure radiation emitted from a beam of 150 MeV protons impinging on a cylindrical PMMA target. Bragg-peak shifts were achieved via adjustment of the PMMA target location and the resulting measurements used during image reconstruction. Reconstructed Bragg peak profiles proved sufficient to observe peak-location differences within 10 mm demonstrating the potential of the MACACO Compton Telescope as a monitoring device for ion-beam therapy.
authors.affiliation: Instituto de Fìsica Corpuscular (IFIC-CSIC/UVEG), Valencia, Spain.
authors.forename: Paola
authors.initials: P
authors.lastname: Solevi
authors.forename: Enrique
authors.initials: E
authors.lastname: Muñoz
authors.forename: Carles
authors.initials: C
authors.lastname: Solaz
authors.forename: Marco
authors.initials: M
authors.lastname: Trovato
authors.forename: Peter
authors.initials: P
authors.lastname: Dendooven
authors.forename: John E
authors.initials: JE
authors.lastname: Gillam
authors.forename: Carlos
authors.initials: C
authors.lastname: Lacasta
authors.forename: Josep F
authors.initials: JF
authors.lastname: Oliver
authors.forename: Magdalena
authors.initials: M
authors.lastname: Rafecas
authors.forename: Irene
authors.initials: I
authors.lastname: Torres-Espallardo
authors.forename: Gabriela
authors.initials: G
authors.lastname: Llosá
mesh_terms: D000465:Algorithms; D003952:Diagnostic Imaging / Q000295:instrumentation*; D005720:Gamma Rays / Q000627:therapeutic use; D006801:Humans; D007091:Image Processing, Computer-Assisted / Q000379:methods*; D009010:Monte Carlo Method; D019047:Phantoms, Imaging; D011522:Protons; D011834:Radiation Monitoring / Q000295:instrumentation*; D061351:Telescopes / Q000706:statistics & numerical data*
chemical_list: D011522:Protons