Potentials for large axial field of view positron camera systems

By extending the axial field-of-view (FOV) in positron emission tomography (PET), the volume sensitivity and the planar sensitivity increase. However, given the current level of commercial block detector technology for the positron camera design, there seems to be little interest in going beyond a 6 or 8 block ring system, corresponding to an axial FOV of 35 to 45 cm, mainly due to cost issues such as the scintillator material and the photomultipliers. A large axial FOV system of the order of one meter or more facilitates a whole body exam in a single bed position, so that multiple organs can be examined simultaneously. Therefore, the dynamic uptake and the bio-distribution of a tracer in different organs could be followed and whole-body kinetics could be studied. The extended axial FOV for PET systems based on Resistive Plate Chambers (RPCs) has been discussed recently. RPC systems provide very good intrinsic spatial and timing resolution. We developed a simple RPC system model by extending our previously described multiblock-ring LSO model to a ∼2 meter axial FOV system and reducing the LSO scintillator depth to provide a singles sensitivity relevant for a RPC detector. The model estimates absolute and planar sensitivity. Based on the planar sensitivity, we estimated the acquisition time needed for the RPC system to achieve comparable image quality with current Siemens Biograph TruePoint and TruePoint TrueV systems (3 and 4 block-rings, respectively). In addition we compared the noise-equivalent count rates (NEC) according to the NEMA NU2-2001 protocol.