MICROPET - A HIGH-RESOLUTION PET SCANNER FOR IMAGING SMALL ANIMALS

MicroPET is a high resolution positron emission tomography (PET) scann er designed for imaging small laboratory animals. It consists of a rin g of 30 position-sensitive scintillation detectors, each with an 8 x 8 array of small lutetium oxyorthosilicate (LSO) crystals coupled via o ptical fibers to a multi-channel photomultiplier tube. The detectors h ave an intrinsic resolution averaging 1.68 mm, an energy resolution be tween 15 and 25% and 2.4 ns timing resolution at 511 keV. The detector ring diameter of microPET is 17.2 cm with an imaging field of view of 112 mm transaxially by 18 mm axially. The scanner has no septa and op erates exclusively in 3D mode. Reconstructed image resolution 1 cm fro m the center of the scanner is 2.0 mm and virtually isotropic, yieldin g a volume resolution of 8 mm(3). For comparison, the volume resolutio n of state-of-the-art clinical PET systems is in the range of 50 - 75 mm(3). Initial images of phantoms have been acquired and are reported. A computer controlled bed is under construction and will incorporate a small wobble motion to improve spatial sampling. This is projected t o further enhance spatial resolution. MicroPET is the first PET scanne r to incorporate the new scintillator LSO and to our knowledge is the highest resolution multi-ring PET scanner currently in existence.