A comparison of three commercially available PET imaging systems

Three commercial positron emission tomography (PET) imagers were assessed using the same test protocol (Positron Corporation 'Posicam', Siemens Ecat 951/31 and the Scanditronix PC 4096-15WB). A cylindrical phantom and a 'Jaszczak' phantom both filled with 18F were employed to measure sensitivity, slice uniformity, transaxial and axial resolution and cold rod contrast. The spread of results were as follows: sensitivity varied from 2.08 to 3.73 kcps kBq-1 ml-1 (77-138 kcps microCi-1 ml-1); radial resolution on axis (at 17.5 cm) varied from 5.0 to 5.9 mm (6.7-8.1 mm); tangential resolution ranged from 5.4 to 5.8 mm (6.7-8.6 mm); axial resolution ranged from 4.6 to 11.5 mm (6.6-13.6 mm); contrast in the middle of a 30 mm diameter rod varied from 98 to 93% and for a 5 mm rod from 37 to 22%. The performance of all three systems approximated reasonably well to the manufacturers' published specifications. The most significant differences were found to be in sensitivity, axial resolution and deadtime correction and can be explained by the choice of crystal size and crystal/photomultiplier configuration.