In-beam imaging performance of the small OpenPET prototype with 11C beam irradiation

The OpenPET geometry is our original idea to visualize a physically opened space between two detector rings. One of the targets is in-beam PET, which is a method for in situ monitoring of charged particle therapy. The OpenPET is expected to be the first practical 3D geometry, while conventional trials using positron cameras are basically limiting to 2D imaging. In the last year, we developed the small prototype. In this study, we carried out detailed in-beam experiments in the Heavy Ion Medical Accelerator in Chiba (HIMAC). The OpenPET prototype (two detector rings of 110 mm diameter separated by a gap of 42 mm) was positioned so that the beam passed through the gap. For usual carbon (12C) beam irradiation, the activity of positron emitters produced through fragmentation reactions is generally low. Instead of the 12C beam, therefore, we used a 11C radioactive beam as an incident beam directly. A PMMA phantom was placed in the center of the FOV, and irradiated along radial direction by the 11C / 12C pencil beam (~30 Gy). For the 11C irradiation, PET images directly corresponding to the distribution of primary particles were obtained with more than ten times higher activity concentration compared with the 12C irradiation.The 6th Japan-Korea Joint Meeting on Medical Physic