Performance evaluation of the microPET P4: a PET system dedicated to animal imaging

The microPET Primate 4-ring system (P4) is an animal PET tomograph with a 7 .8 cm axial extent, a 19 cm diameter transaxial field of view (FOV) and a 2 2 cm animal port. The system is composed of 168 detector modules. each with an 8 x 8 array of 2.2 x 2.2 x 10 mm(3) lutetium oxyorthosilicate crystals, arranged as 32 crystal rings 26 cin in diameter. The detector crystals are coupled to a Hamamatsu R5900-C8 PS-PMT via a 10 cm long optical fibre bund le. The detectors have a timing resolution of 3.2 ns, an average energy res olution of 26%, and an average intrinsic spatial resolution of 1.75 mm. The system operates in 3D mode without inter-plane septa. acquiring data in li st mode. The reconstructed image spatial resolution ranges from 1.8 min at the centre to 3 mm at 4 cm radial offset. The tomograph has a peak system s ensitivity of 2.25% at the centre of the FOV with a 250-750 keV energy wind ow. The noise equivalent count rate peaks at 100-290 kcps for representativ e object sizes. Images from two phantoms and three different types of labor atory animal demonstrate the advantage of the P4 system over the original p rototype microPET. including its threefold improvement in sensitivity and a large axial FOV sufficient to image an entire mouse in a single bed positi on.