A method of tagging the nuclear fragmentation event induced by ¹¹C for cancer therapy

Heavy ion cancer therapy using energetic ¹²C ions has been carried out successfully at the Heavy Ion Medical Accelerator in Chiba (HIMAC), Japan. The method has advantages over traditional radiation therapy using an energetic photon beam in two respects: the dose concentration owing to the Bragg peak and high biological effects. The development of a cancer therapy using ¹¹C ions is also currently underway at HIMAC, however, there remains the problem of beam attenuation due to nuclear fragmentation reactions in the body of the patient; this requires modification of the dose calculation for the therapy. To the best of our knowledge, no research on ¹¹C-induced nuclear fragmentation reactions has yet been published. We propose a method of identifying the nuclear fragmentation reaction event induced by the carbon beams using a total-absorption-type target detector, that plays the role of a human phantom, and a system of plastic scintillation counters surrounding the phantom. We have carried out measurements for the carbon beams with the detector system. A portion of the beam energy is lost as escaping fragment particles from the phantom, leading to a decrease in beam intensity. We were able to successfully detect nuclear reaction events on an event-by-event basis.