title: The biological effectiveness of antiproton irradiation.
abstract: OBJECTIVE
  Antiprotons travel through tissue in a manner similar to that for protons until they reach the end of their range where they annihilate and deposit additional energy. This makes them potentially interesting for radiotherapy. The aim of this study was to conduct the first ever measurements of the biological effectiveness of antiprotons.
  
  
  METHODS
  V79 cells were suspended in a semi-solid matrix and irradiated with 46.7MeV antiprotons, 48MeV protons, or (60)Co gamma-rays. Clonogenic survival was determined as a function of depth along the particle beams. Dose and particle fluence response relationships were constructed from data in the plateau and Bragg peak regions of the beams and used to assess the biological effectiveness.
  
  
  RESULTS
  Due to uncertainties in antiproton dosimetry we defined a new term, called the biologically effective dose ratio (BEDR), which compares the response in a minimally spread out Bragg peak (SOBP) to that in the plateau as a function of particle fluence. This value was approximately 3.75 times larger for antiprotons than for protons. This increase arises due to the increased dose deposited in the Bragg peak by annihilation and because this dose has a higher relative biological effectiveness (RBE).
  
  
  CONCLUSIONS
  We have produced the first measurements of the biological consequences of antiproton irradiation. These data substantiate theoretical predictions of the biological effects of antiproton annihilation within the Bragg peak, and suggest antiprotons warrant further investigation.
authors.affiliation: Pbar Labs, LLC, Santa Fe, NM, USA.
authors.forename: Michael H
authors.initials: MH
authors.lastname: Holzscheiter
authors.forename: Niels
authors.initials: N
authors.lastname: Bassler
authors.forename: Nzhde
authors.initials: N
authors.lastname: Agazaryan
authors.forename: Gerd
authors.initials: G
authors.lastname: Beyer
authors.forename: Ewart
authors.initials: E
authors.lastname: Blackmore
authors.forename: John J
authors.initials: JJ
authors.lastname: DeMarco
authors.forename: Michael
authors.initials: M
authors.lastname: Doser
authors.forename: Ralph E
authors.initials: RE
authors.lastname: Durand
authors.forename: Oliver
authors.initials: O
authors.lastname: Hartley
authors.forename: Keisuke S
authors.initials: KS
authors.lastname: Iwamoto
authors.forename: Helge V
authors.initials: HV
authors.lastname: Knudsen
authors.forename: Rolf
authors.initials: R
authors.lastname: Landua
authors.forename: Carl
authors.initials: C
authors.lastname: Maggiore
authors.forename: William H
authors.initials: WH
authors.lastname: McBride
authors.forename: Søren Pape
authors.initials: SP
authors.lastname: Møller
authors.forename: Jørgen
authors.initials: J
authors.lastname: Petersen
authors.forename: Lloyd D
authors.initials: LD
authors.lastname: Skarsgard
authors.forename: James B
authors.initials: JB
authors.lastname: Smathers
authors.forename: Timothy D
authors.initials: TD
authors.lastname: Solberg
authors.forename: Ulrik I
authors.initials: UI
authors.lastname: Uggerhøj
authors.forename: Sanja
authors.initials: S
authors.lastname: Vranjes
authors.forename: H Rodney
authors.initials: HR
authors.lastname: Withers
authors.forename: Michelle
authors.initials: M
authors.lastname: Wong
authors.forename: Bradly G
authors.initials: BG
authors.lastname: Wouters
mesh_terms: D000818:Animals; D002470:Cell Survival / Q000528:radiation effects*; D002478:Cells, Cultured / Q000528:radiation effects; D003037:Cobalt Radioisotopes; D003114:Colony-Forming Units Assay; D006224:Cricetinae; D004307:Dose-Response Relationship, Radiation; D005720:Gamma Rays; D011522:Protons; D012062:Relative Biological Effectiveness
chemical_list: D003037:Cobalt Radioisotopes; D011522:Protons