Methods to optimize whole body surveys with the C-PET camera

An optimized FDG PET survey of the human body should acquire data near peak camera performance. This is achieved by a knowledge of patient activity distributions and tumor uptake as well as camera performance characteristics. The C-PET camera has been used to perform both patient-matched phantom and clinical measurements. Phantom measurements of camera resolution, countrates, noise, signal-to-noise ratio (SNR) and contrast have been performed as a function of activity and scan duration. Measurements of body countrates and normal organ, whole body and tumor activity have been performed on patient data as a function of dose, uptake period and volume in the FOV. Peak NEC is reached at a singles countrate of 5 Mcps. However, image nonuniformity, contrast and SNR are optimal at 3 Mcps. At this countrate camera resolution is not significantly degraded while measured SNR and contrast for a torso-sized phantom are near their optimal values. Noise for head and leg matched phantoms are lower due to the reduced attenuation and scatter for these objects. Emission scan durations of 4 mins for the head and torso and 2 min for the legs result in only moderately reduced SNR compared to 10 min scans. Torso SUVs are constant across patients and uptake periods. Normal lung, liver, heart and kidney uptake remain constant to ±10% between 70 and 120 mins post-injection, while tumor uptakes increase by 30% over this period, showing the value of delayed imaging. In conclusion, an optimized FDG PET survey requires injection of 2.6 MBq/kg of ¹⁸F, a 60 minute uptake period and survey from knees to head (140 cm axially) within 60 minutes. In this way overall activities, countrates and SNRs are optimized. At the same time tumor uptakes are sampled near their peak while background activities are saturated or declining