We report on the design of a small animal PET scanner based on continuous LYSO crystals and position sensitive photomultiplier tubes (PSPMTs), together with the first results from the calibration. The scanner consists of eight compact modules forming an octagon and leaving a port of 110 mm aperture. Each module is made out of a continuous LYSO crystal and a PSPMT, and contains its associated electronics together with its power supply. For each module, five signals are read, summarizing all the information coming out from its 64 anode pads. Therefore, for the whole scanner only 40 signals are digitized. A calibration procedure has been implemented, measuring a spatial resolution of approximately 1.5 mm at the center of the field of view and an energy resolution of 18%. The sensitivity of the system at the center of the field of view, using only 4 modules, is observed to be of about 1%.