Abstract
At the National Institute of Radiological Sciences, we are developing OpenPET, an open-type positron emission tomography (PET) geometry with a physically open space, which allows easy access to the patient during PET studies. Our first-generation OpenPET system, dual-ring OpenPET, which consisted of two detector rings, could provide an extended axial field of view (FOV) including the open space. However, for applications such as in-beam PET to monitor the dose distribution in situ during particle therapy, higher sensitivity concentrated on the irradiation field is required rather than a wide FOV. In this report, we propose a second-generation OpenPET geometry, single-ring OpenPET, which can efficiently improve sensitivity while providing the required open space. When the proposed geometry was realized with block detectors, position-dependent degradation of the spatial resolution was expected because it was necessary to arrange the detector blocks in ellipsoidal rings stacked and shifted relative to one another. However, we found by Monte Carlo simulation that the use of depth-of-interaction (DOI) detectors made it feasible to achieve uniform spatial resolution in the FOV.
