Simulation study of Resistive-Plate-Chambers based PET for hadron-therapy monitoring

This is a preliminary study on the feasibility of using Resistive-Plate-Chambers (RPC) based Positron Emission Tomography (PET) for hadron-therapy monitoring. The imaging capabilities of the RPC gas detector are being investigated for PET. Their main advantages are excellent timing resolution, low cost and Depth Of Interaction information (DOI) due to their layered structure. Hadron-therapy (HT) aims at treating tumors by maximizing the dose released to the target and sparing healthy tissue. During irradiation with a hadron beam, fragments, positron emitting isotopes and gamma radiation are produced. This radiation coming from the tissue activation could be used for quality control of the treatment. Our work focuses on imaging the positron emitting isotopes using an RPC-based PET scanner. The low cost of RPC makes possible to enlarge the angular coverage of the scanner guaranteeing the higher sensitivity needed by the in-beam monitoring. In addition, the TOF capability and spatial resolution makes worth investigating it. A first protoype is currently under construction at CERN in the TERA group. For this study, Monte Carlo simulations by means of GATE were employed. Up on our knowledge, such gas detectors have not been simulated yet in GATE and the new version of GATE offers new tools for dosimetry. These are the main reasons of choosing GATE. A set of linear sources, simulating the delivery of a hadron beam, has proposed to evaluate the image quality for an ideal time resolution of the system and the TOF information is being considered in the reconstruction. For the full ring simulated system, no important differences were found between TOF and non-TOF images, only the contrast was always better for the TOF-images. However, further simulations should be performed adapting the system to the real situation (partial ring) for HT and lowering the detected events to a clinical number. Under these circumstances, we expect to be crucial the TOF capabilities of the RPC-PET.