title: Sensitivity study of prompt gamma imaging of scanned beam proton therapy in heterogeneous anatomies.
abstract: OBJECTIVE
  To investigate the use of a fast analytical prediction algorithm in the evaluation of the accuracy in Bragg peak position estimation using prompt gamma imaging in realistic anatomies.
  
  
  METHODS
  Brain, nasal cavity and lung spot scanning treatments were planned on an anthropomorphic phantom. Plan delivery in a clinical proton therapy facility was monitored using a prompt gamma camera. A pencil-beam algorithm was developed to simulate prompt gamma acquisition. For each spot, the sensitivity to setup and CT conversion errors was evaluated based on error scenarios.
  
  
  RESULTS
  Good agreement was found between simulations and measurements (average shift of 0.4mm on whole-layer profiles). The spots with greatest sensitivity to setup or CT conversion errors could be identified. The comparison between expected and estimated shifts showed that the errors in shift estimation due to heterogeneities were in average lower than 1mm in all cases except the lung. In the lung case, only 40% of the spots showed accuracy better than 2mm.
  
  
  CONCLUSIONS
  The analytical prediction algorithm was successfully used to simulate prompt gamma acquisitions of scanned treatment plans. The accuracy in Bragg peak position estimation was generally sub-millimeter in heterogeneous anatomies, except in lung tissues.
authors.affiliation: Ion Beam Applications SA, Louvain-la-Neuve, Belgium.
authors.forename: Guillaume
authors.initials: G
authors.lastname: Janssens
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.
authors.forename: François
authors.initials: F
authors.lastname: Vander Stappen
authors.affiliation: Ion Beam Applications SA, Louvain-la-Neuve, Belgium.
authors.forename: Damien
authors.initials: D
authors.lastname: Prieels
authors.affiliation: Université catholique de Louvain, iMagX Project, ICTEAM Institute, Louvain-la-Neuve, Belgium.
authors.forename: Enrico
authors.initials: E
authors.lastname: Clementel
authors.affiliation: Université catholique de Louvain, iMagX Project, ICTEAM Institute, Louvain-la-Neuve, Belgium.
authors.forename: Eugen-Lucian
authors.initials: EL
authors.lastname: Hotoiu
authors.affiliation: Université catholique de Louvain, Center of Molecular Imaging, Radiotherapy and Oncology, Institut de Recherche Expérimentale et Clinique, Brussels, Belgium. Electronic address: edmond.sterpin@uclouvain.be.
authors.forename: Edmond
authors.initials: E
authors.lastname: Sterpin
mesh_terms: D000465:Algorithms; D001932:Brain Neoplasms / Q000000981:diagnostic imaging / Q000532:radiotherapy; D015902:Gamma Cameras; D005720:Gamma Rays; D006801:Humans; D008175:Lung Neoplasms / Q000000981:diagnostic imaging / Q000532:radiotherapy; D009669:Nose Neoplasms / Q000000981:diagnostic imaging / Q000532:radiotherapy; D019047:Phantoms, Imaging; D061766:Proton Therapy / Q000379:methods*; D011880:Radiotherapy Planning, Computer-Assisted / Q000379:methods*
keywords: Prompt gamma imaging; Proton range verification; Range uncertainties