SPEM: A state-of-the-art instrument for high resolution molecular imaging of small animal organs

Objective: To describe the Single Photon Emission Microscope(SPEM), a state-of-the-art instrument for small animal SPECT imaging,and characterize its performance presenting typical images of differentanimal organs. Methods: SPEM consists of two independent imagingdevices based on high resolution scintillators, high sensitivity andresolution Electron-Multiplying CCDs and multi-pinhole collimators.During image acquisition, the mouse is placed in a rotational verticalholder between the imaging devices. Subsequently, an appropriatesoftware tool based on the Maximum Likelihood algorithm iterativelyproduces the volumetric image. Radiopharmaceuticals for imagingkidneys, heart, thyroid and brain were used. The mice were injectedwith 74 to 148 MBq/0,3mL and scanned for 40 to 80 minutes, 30to 60 minutes afterwards. During this procedure, the animalsremained under ketamine/xilazine anesthesia. Results: SPEM imagesof different mouse organs are presented, attesting the imagingcapabilities of the instrument. Conclusion: SPEM is an innovativetechnology for small animal SPECT imaging providing high resolutionimages with appropriate sensitivity for pre-clinical research. Its usewith appropriate radiotracers will allow translational investigationof several animal models of human diseases, their pharmacologicaltreatment and the development of potential new therapeutic agents.