Positron emission tomography scanner with a 19 cm (transaxial) by 7.6 cm (axial) field of view. The system has an absolute sensitivity of 4% with a spatial resolution of ~1.3 mm at the center of the field of view. List-mode data acquisition allows acquired data to be processed in a static or dynamic fashion to provide quantitative snapshots or summed sequences of radioactivity distribution in live animals. An interchangeable bed allows successive PET/CT scans of small animals to provide structural and metabolic data similar to PET/CT scans in clinical scenarios without the need for additional fusion or morphing software manipulations. Non-invasive, in vivo functional imaging with microPET® allows both serial and longitudinal studies to be conducted in the same animal.