The AD-4/ACE collaboration at CERN is investigating the anticipated benefit of antiproton radiotherapy. The experimental tasks have been twofold: 1) To quantify the radiobiological properties of the antiproton beam. 2) Perform absolute dosimetry on a pulsed antiproton beam. In order to do define the biological properties of antiprotons it is inevitable that we have adequate dosimetry of the antiproton beam. This is complicated in the peak-region by the mixed particle field from the antiproton annihilation. A beam of antiprotons will behave similar as a proton beam at high velocities, but when the antiprotons stop, they annihilate on a nuclei of the target material, producing high energy gamma's, pions, neutrons, and recoil ions. A portion of the energy released hereby is observed as an augmentation of the well known proton Bragg peak. We have performed dosimetry experiments and investigated the radiobiological properties using antiprotons at 50 and 125 MeV from the Antiproton Decelerator (AD) at CERN. Dosimetry experiments were carried out with ionization chambers, alanine pellets and radiochromic film. Radiobiological experiments were done with Chinese V79 WNRE hamster cells. Monte Carlo particle transport codes were investigated and compared with results obtained from the ionization chambers and alanine pellets. A track structure model have been applied on the calculated particle spectrum, and been used to predict the LET-dependent response of the alanine pellets. The particle transport program FLUKA produced data which were in excellent agreement with our ionization chamber measurements, and in good agreement with our alanine measurements. FLUKA is now being used to generate a wide range of depth dose data at several energies, including secondary particle–energy spectra, which will be used as base data for a treatment planning software such as TRiP for further studies of expected clinical consequences. This can also be used to compare antiprotons to carbon ions and protons in realistic treatment situations.
Ion Beams in Biology and Medicine: 39. Annual Conference of the German-swiss Association for Radiation Protection and 11th Workshop of Heavy Charged Particles in Biology and Medicine, Heidelberg, 26th-29th September 2007, 2007, p. 117-121