title: The relative biological effectiveness of antiprotons.
abstract: Aside from the enhancement of physical dose deposited by antiprotons annihilating in tissue-like material compared to protons of the same range a further increase of biological effective dose has been demonstrated. This enhancement can be expressed in an increase of the relative biological effectiveness (RBE) of antiprotons near the end of range. We have performed the first-ever direct measurement of the RBE of antiprotons both at rest and in flight.
  
  
  
  Experimental data were generated on the RBE of an antiproton beam entering a tissue-like target consisting of V79 cells embedded in gelatin with an energy providing a range of approximately 10cm.
  
  
  
  The RBE in the entrance channel (the "plateau") is only slightly above the value for a comparable proton beam, and remains low until the proximal edge of the spread-out Bragg peak (SOBP). A steep increase of RBE is seen starting from the onset of the SOBP.
  
  
  
  This paper reports the final results of the experiment AD-4/ACE at CERN on the first-ever direct measurement of RBE of antiprotons and constitutes the first step toward developing treatment plans.
authors.affiliation: Department of Physics and Astronomy, University of New Mexico, Albuquerque, USA; Max Planck Institute for Nuclear Physics, Heidelberg, Germany. Electronic address: michael.holzscheiter@gmail.com.
authors.forename: Michael H
authors.initials: MH
authors.lastname: Holzscheiter
authors.affiliation: Department of Experimental Clinical Oncology, Aarhus University Hospital, Denmark.
authors.forename: Jan
authors.initials: J
authors.lastname: Alsner
authors.affiliation: Department of Experimental Clinical Oncology, Aarhus University Hospital, Denmark; Department of Physics and Astronomy, Aarhus University, Denmark.
authors.forename: Niels
authors.initials: N
authors.lastname: Bassler
authors.affiliation: Max Planck Institute for Nuclear Physics, Heidelberg, Germany.
authors.forename: Rebecca
authors.initials: R
authors.lastname: Boll
authors.affiliation: Dipartimento di Scienza e Alta Tecnologia, Universita degli Studi dell'Insubria, Como, Italy.
authors.forename: Massimo
authors.initials: M
authors.lastname: Caccia
authors.affiliation: Department of Physics and Astronomy, Aarhus University, Denmark.
authors.forename: Helge
authors.initials: H
authors.lastname: Knudsen
authors.forename: Carl
authors.initials: C
authors.lastname: Maggiore
authors.affiliation: Department of Experimental Clinical Oncology, Aarhus University Hospital, Denmark.
authors.forename: Jørgen B
authors.initials: JB
authors.lastname: Petersen
authors.affiliation: Max Planck Institute for Nuclear Physics, Heidelberg, Germany.
authors.forename: Stefan
authors.initials: S
authors.lastname: Sellner
authors.affiliation: Max Planck Institute for Nuclear Physics, Heidelberg, Germany.
authors.forename: Tina
authors.initials: T
authors.lastname: Straße
authors.affiliation: Department of Experimental Clinical Oncology, Aarhus University Hospital, Denmark.
authors.forename: Brita
authors.initials: B
authors.lastname: Singers Sørensen
authors.affiliation: Department of Experimental Clinical Oncology, Aarhus University Hospital, Denmark.
authors.forename: Jens
authors.initials: J
authors.lastname: Overgaard
mesh_terms: D004601:Elementary Particles / Q000627:therapeutic use*; D006801:Humans; D009010:Monte Carlo Method; D009369:Neoplasms / Q000532:radiotherapy; D061766:Proton Therapy; D011874:Radiometry / Q000379:methods; D011879:Radiotherapy Dosage; D011882:Radiotherapy, High-Energy / Q000379:methods*; D012062:Relative Biological Effectiveness; D011522:Protons
chemical_list: D011522:Protons
keywords: Antiprotons; Particle therapy; Relative biological effectiveness (RBE)