Patient-specific apertures are routinely used in double scattering (DS) proton therapy (PT) to laterally conform the beam to the tumor. This study investigates the potential use of these devices in pencil beam scanning (PBS) PT. Geant4 Monte Carlo simulations were performed to determine the out-of-field doses in DS and PBS with and without an aperture for a typical prostate field configuration. The out-of-field doses are lower in PBS than DS except near the field edge, due to the wider lateral penumbra in PBS. Using an aperture in PBS reduces the penumbral width and the out-of-field doses. Close to the field edge, the doses can be reduced by over an order of magnitude. A small increase in the neutron dose (due to proton interactions with the aperture) is offset by a larger reduction in proton dose. Employing a patient-specific aperture can improve conformality and reduce the out-of-field doses in PBS PT.
Physics in Medicine & Biology
Apr 30, 2012
Monte Carlo study of the potential reduction in out-of-field dose using a patient-specific aperture in pencil beam scanning proton therapy
S J Dowdell, B Clasie, N Depauw, P Metcalfe, A B Rosenfeld, H M Kooy, J Flanz and H Paganetti 2012 Phys. Med. Biol. 57 2829
About the author
Stephen J Dowdell (University of Wollongong, NSW, Australia, and Massachusetts General Hospital and Harvard Medical School, Boston, USA), Benjamin Clasie (Massachusetts General Hospital and Harvard Medical School, Boston, USA), Nicolas Depauw (University of Wollongong, NSW, Australia, and Massachusetts General Hospital and Harvard Medical School, Boston, USA), Peter Metcalfe, Anatoly B Rosenfeld (University of Wollongong, NSW, Australia), Hanne M Kooy, Jacob B Flanz and Harald Paganetti (Massachusetts General Hospital and Harvard Medical School, Boston, USA)