A simulation study of a long axial field of view whole-body PET scanner using cylindrical and anthropomorphic phantoms

Clinical whole-body PET scanners mostly have an axial field of view (AFOV) ranging from 15-21 em in length, which limits sensitivity and prevents the acquisition of wholebody dynamic images. We present results from a simulation study for a fully 3D, 2 meter long AFOV whole body PET scanner where we use cylindrical and anthropomorphic phantoms to characterize the count-rate performance using noise equivalent counts (NEC) as the metric. For whole-body scanners with a conventional AFOV, the NEC is generally expected to increase when data from larger ring differences is accepted. However, the lines of response with large ring difference values may encounter a large amount of tissue and attenuation, which may limit the number of trues detected without a concomitant reduction in scatter and randoms, thus limiting NEC. When the activity level in the phantom increases, the dead-time and randoms also increase significantly, eventually reducing the NEC performance as well. In this simulation study, the NEC was computed as a function of maximum acquired ring difference and activity for each phantom to find optimal performance parameters for our proposed scanner. Our simulation results show our proposed scanner performs 25-50 times better than existing clinical scanners in terms of NEC performance. With significant gains in sensitivity, a long AFOV scanner can potentiaUy be used for whole body dynamic PET studies.