IOP PUBLISHING PHYSICS IN MEDICINE AND BIOLOGY Phys. Med. Biol. 53 (2008) 793–805 doi:10.1088/0031-9155/53/3/017 The antiproton depth–dose curve in water N Bassler 1,2 , M H Holzscheiter 3 ,OJ¨ akel 2 , H V Knudsen 4 , S Kovacevic 5 and (the AD-4/ACE Collaboration) 6 1 Department of Experimental Clinical Oncology, Aarhus University Hospital, Aarhus, Denmark 2 Deutsches Krebsforschungszentrum, Heidelberg, Germany 3 University of New Mexico, Albuquerque, NM, USA 4 Department of Physics and Astronomy, University of Aarhus, Aarhus, Denmark 5 University of Montenegro, Podgorica, Montenegro E-mail: n.bassler@dkfz.de Received 19 September 2007, in final form 2 December 2007 Published 14 January 2008 Online at stacks.iop.org/PMB/53/793 Abstract We have measured the depth–dose curve of 126 MeV antiprotons in a water phantom using ionization chambers. Since the antiproton beam provided by CERN has a pulsed structure and possibly carries a high-LET component from the antiproton annihilation, it is necessary to correct the acquired charge for ion recombination effects. The results are compared with Monte Carlo calculations and were found to be in good agreement. Based on this agreement we calculate the antiproton depth–dose curve for antiprotons and compare it with that for protons and find a doubling of the physical dose in the peak region for antiprotons. (Some figures in this article are in colour only in the electronic version) 1. Introduction The basic idea of antiproton radiotherapy (Gray and Kalogeropoulos 1984) is to utilize the energy from the antiproton–nucleus annihilation reactions, which occur when the antiprotons come to rest. Antiprotons behave similar to protons at high velocities, but when they slow 6 M H Holzscheiter 1, N Bassler 2, 3, J Alsner 2, G Beyer 4, J J DeMarco 5, M Doser 6, D Hajdukovic 7, O Hartley 4, K S Iwamoto 5, O J¨ akel 3, H V Knudsen 8, S Kovacevic 7, S Pape Møller 9, J Overgaard 2, J B Petersen 2, T D Solberg 10, S Vranjes 11, B G Wouters 12. 1. University of New Mexico, Albuquerque, NM, USA; 2. Department of Medical Physics and Experimental Clinical Oncology, Aarhus University Hospital, Aarhus, Denmark; 3. Deutsches Krebsforschungszentrum, Heidelberg, Germany; 4. Hospital Universitaire de Geneve, Geneva, Switzerland; 5. David Geffen School of Medicine, UCLA, Los Angeles, CA, USA; 6. CERN, Geneva, Switzerland; 7. University of Montenegro, Podgorica, Montenegro; 8. Department of Physics & Astronomy, University of Aarhus, Aarhus, Denmark; 9. ISA, University of Aarhus, Aarhus, Denmark; 10. University of Nebraska Medical Center, Omaha, NE, USA; 11. VINCA Institute for Nuclear Sciences, Belgrade, Serbia; 12. University of Maastricht, Res. Institute Growth and Development, The Netherlands. 0031-9155/08/030793+13$30.00 © 2008 Institute of Physics and Engineering in Medicine Printed in the UK 793