A tumor detection observer study comparing 2D versus 3D whole-body PET imaging protocols

In this work the authors compare the impact of the acquisition mode (2D vs. 3D) on the performance of human observers in detecting and localizing tumors. They use a non-Monte Carlo simulator to rapidly generate multiple realizations of ideal data with added spherical lesions and with accurate noise properties, thus avoiding the confounding effect of residual biases. The simulated 2D data sets were reconstructed using 2D attenuation-weighted OSEM and the 3D data sets were first rebinned using FORE and then reconstructed with AWOSEM. To define an optimal protocol for each mode, the authors performed 2D and 3D acquisitions of an anthropomorphic phantom on a Siemens/CTI HR+ scanner and measured the NEC rate as a function of the activity concentration in the phantom for different organs. The peak value in 3D was achieved for an injected dose of approximately 12 mCi, whereas the 2D peak value was never reached. The simulation count rates were therefore set to those corresponding to a 12 mCi injected dose in 3D and 2D and the authors also analysed the case equivalent to a 20 mCi injected dose in 2D which was considered as the maximum allowable dose based on considerations of dosimetry and cost.