title: Out-of-field dose studies with an anthropomorphic phantom: comparison of X-rays and particle therapy treatments.
abstract: OBJECTIVE
  Characterization of the out-of-field dose profile following irradiation of the target with a 3D treatment plan delivered with modern techniques.
  
  
  METHODS
  An anthropomorphic RANDO phantom was irradiated with a treatment plan designed for a simulated 5 × 2 × 5 cm(3) tumor volume located in the center of the head. The experiment was repeated with all most common radiation treatment types (photons, protons and carbon ions) and delivery techniques (Intensity Modulated Radiation Therapy, passive modulation and spot scanning). The measurements were performed with active diamond detector and passive thermoluminescence (TLD) detectors to investigate the out-of-field dose both inside and outside the phantom.
  
  
  RESULTS
  The highest out-of-field dose values both on the surface and inside the phantom were measured during the treatment with 25 MV photons. In the proximity of the Planned Target Volume (PTV), the lowest lateral dose profile was observed for passively modulated protons mainly because of the presence of the collimator in combination with the chosen volume shape. In the far out-of-field region (above 100mm from the PTV), passively modulated ions were characterized by a less pronounced dose fall-off in comparison with scanned beams. Overall, the treatment with scanned carbon ions delivered the lowest dose outside the target volume.
  
  
  CONCLUSIONS
  For the selected PTV, the use of the collimator in proton therapy drastically reduced the dose deposited by ions or photons nearby the tumor. Scanning modulation represents the optimal technique for achieving the highest dose reduction far-out-of-field.
authors.affiliation: GSI Helmholtzzentrum für Schwerionenforschung GmbH, Darmstadt, Germany. c.latessa@gsi.de
authors.forename: Chiara
authors.initials: C
authors.lastname: La Tessa
authors.forename: Thomas
authors.initials: T
authors.lastname: Berger
authors.forename: Robert
authors.initials: R
authors.lastname: Kaderka
authors.forename: Dieter
authors.initials: D
authors.lastname: Schardt
authors.forename: Christine
authors.initials: C
authors.lastname: Körner
authors.forename: Ulla
authors.initials: U
authors.lastname: Ramm
authors.forename: Jörg
authors.initials: J
authors.lastname: Licher
authors.forename: Nakahiro
authors.initials: N
authors.lastname: Matsufuji
authors.forename: Christina
authors.initials: C
authors.lastname: Vallhagen Dahlgren
authors.forename: Tony
authors.initials: T
authors.lastname: Lomax
authors.forename: Günther
authors.initials: G
authors.lastname: Reitz
authors.forename: Marco
authors.initials: M
authors.lastname: Durante
mesh_terms: D000886:Anthropometry; D006801:Humans; D019047:Phantoms, Imaging; D011522:Protons; D011874:Radiometry; D050397:Radiotherapy, Intensity-Modulated; D013819:Thermoluminescent Dosimetry; D014965:X-Rays
chemical_list: D011522:Protons