Application of proton boron fusion to proton therapy: Experimental verification to detect the alpha particles

Feasibility of proton boron fusion (PBF) reaction to radiotherapy has previously been studied using Monte Carlo simulation. Alpha particles are emitted from the fusion reaction between the proton and 11B close to the end of the Bragg peak. The generated alpha particles can theoretically induce critical damage to tumor cells due to their high linear energy transfer. Nevertheless, there has been a lack of experimental verification to detect the alpha particles and to apply in proton therapy due to the difficulty to observe the generated alpha particles with a very short range in medium. An experimental observation of the generation of alpha particles is indeed necessary for PBF to be applied to proton therapy. We have performed an experimental study using a medical proton accelerator and fine-grained nuclear emulsion films to detect tracks of alpha particles produced. These films, attached to the rear side of the natural boron containing plate located close to the end of the Bragg peak, were individually irradiated by 2 × 108 cm−2 density proton beams at an energy of 79.7 MeV. Some clear tracks of alpha particles, produced by the PBF reaction and clearly separated with those from n + 10B reaction, were observed with the use of a 3D microscope after the films were developed. Each track was analyzed, and alpha particle tracks were verified. A detailed experimental method will be presented using microscopy analysis. In conclusion, the experimental results showed that the observation of alpha particles resulted from PBF and the application feasibility of the PBF reaction to the proton therapy.Feasibility of proton boron fusion (PBF) reaction to radiotherapy has previously been studied using Monte Carlo simulation. Alpha particles are emitted from the fusion reaction between the proton and 11B close to the end of the Bragg peak. The generated alpha particles can theoretically induce critical damage to tumor cells due to their high linear energy transfer. Nevertheless, there has been a lack of experimental verification to detect the alpha particles and to apply in proton therapy due to the difficulty to observe the generated alpha particles with a very short range in medium. An experimental observation of the generation of alpha particles is indeed necessary for PBF to be applied to proton therapy. We have performed an experimental study using a medical proton accelerator and fine-grained nuclear emulsion films to detect tracks of alpha particles produced. These films, attached to the rear side of the natural boron containing plate located close to the end of the Bragg peak, were individually ir...