Washout studies of in-beam rat imaging by the 2nd generation OpenPET prototype

In-beam positron emission tomography (PET) is expected to be suitable as an in situ dose verification technique in particle therapies. For accurate dose verification, washout of positron emitters should be corrected. In addition, the quantitative washout rate has a potential usefulness as a diagnostic index such as for blood flow and stage of cancer progression. In this work, therefore, we applied compartment analyses to in-beam PET data acquired by the 2nd generation small OpenPET prototype. The OpenPET is our original idea for the open-type PET geometries, which enables PET scanning during irradiation in particle therapies. Two rat brains and two rat thighs located at the field-of-view were irradiated by a 11C beam. Time activity curves of the irradiated field were measured immediately after the irradiations, and the washout rate was calculated based on the two-washout model (medium decay, k2m; slow decay, k2s) developed in a previous study of rabbit irradiation reported by Mizunoet al. For brain irradiations, k2m and k2s were respectively, 0.37 and 0.008 [min-1]. For thigh irradiations, these were 0.34 and 0.008 [min-1]. These results were consistent with the rabbit study. Also k2m of brain irradiation was close to the washout rate in cerebral blood flow measurements by dynamic PET with 15O-water. Our present work suggested the k2m may be relevant to blood flow.2013 IEEE NSS/MIC/PTS