Multi-scanner PET 2D/3D comparison with cerebral FDG

A comparison was made of 2D and 3D FDG cerebral PET scans acquired on human subjects on two different PET scanners, a CTI ECAT HR+ and a GE Advance. The two scan protocols were part of independent studies and involved a 30 (20) minute 2D scan, a 10 (5) minute transmission scan after (before) injection, and a 10 (10) minute 3D scan for the Advance (HR+). Image reconstruction used each vendor´s standard recommendations. The HR+ showed good correlation between 2D and 3D modes, whereas the Advance systematically showed up to a 20% difference between modes, with larger discrepencies for higher pixel values. However, after a major upgrade to the GE/Advance that included replacing all of the detector units, a marked improvement in the 3D quantitative accuracy was noted. A head-sized phantom containing a warm background and various sizes of hot and cool spheres (9, 17, 22mm) was scanned in both scanners. The concentration (0.5 - 0.8 microCi/ml) and volume (∼3 liters) were designed to mimic a typical cerebral FDG scan, and a range of scan durations (1-30 minutes) were acquired to span the range of most FDG protocols. The correlation between 2D and 3D modes showed a similar pattern for each scanner as for the human data. However, the Advance showed somewhat better reliability and slightly better accuracy for recovering activity within the small spheres in 3D mode.