Comparison of NEC and subjective image quality measures in 2D and 3D whole-body PET imaging

Twelve clinical 3D whole-body PET studies have been used to compute noise-effective counts (NEC) for comparison with observer study results. Clinical data was collected using data acquired on a GE Advance/spl trade/ PET imaging system. Data acquisition for the studies was performed by acquisition of multi-frame 2D & 3D emission data along with a transmission scan. Patient weights ranged from 112 lb to 320 lb (average=178 lb); injected activity ranged from 7.7-12.9mCi (average=10.1); 2D and 3D post-injection frame acquisition start times averaged 74 and 125 minutes respectively. NEC was calculated using a k factor based upon the fraction of randoms within the patient boundary, found by segmentation of the transmission sinograms, and assuming real-time randoms subtraction.