Single Photon Emission Computed Tomography (SPECT) allows to visualize and quantify uptake and biodistribution of gamma-radiation emitting radiotracers in vivo. SPECT imaging in small animals requires high resolution as well as sensitivity, which can be accomplished with dedicated systems, such as the NanoSPECT/CT (Mediso). This system employs multi-pinhole collimators projecting multiple overlapping images onto four scintillation cameras. During a subsequent reconstruction, a single three-dimensional image is recalculated, boosting the overall sensitivity. Depending on the pinhole diameter, resolutions of less than 0.5 mm can be achieved however at the cost of increased acquisition time. For the anatomical reference, the system is equipped with a microCT unit with a resolution of about 80 µm.

Acquisition of consecutive SPECT scans allows to image pharmacokinetic of radiolabeled compounds. For a single field of view, acquisition time can be as short as four minutes depending on the injected activity, used collimators and required resolution. The energy resolving detectors allow to simultaneously quantify and visualize biodistribution of two different radionuclides in vivo. Further, SPECT/CT imaging was successfully used to study the pharmacokinetics and biodistribution of various therapeutic compounds such as peptides, antibodies, liposomes of ultrasound activatable microbubbles.