ECG-gated pinhole SPECT in mice with millimeter spatial resolution

We have developed a single photon emission computed tomography (SPECT) tech nique for high resolution radiotracer imaging of mice where the object is r otated instead of the scintillation camera. The system uses a 21 cm focal l ength pinhole collimator with a 0.5 mm diameter aperture, resulting in magn ification ranging from 7 to 10 and acquisition times from 60 to 90 minutes. This method employs a plastic mouse-holding tube designed to address speci fic problems associated with pinhole SPECT, including low count rates and c orrection for shift of the center of rotation. Images of a novel "mouse hea rt" phantom demonstrated good image quality, uniformity, and spatial resolu tion. A Tc-99m-sestamibi scan of a normal mouse, electrocardiogram-gated at over 400 beats per minute, allowed assessment of regional myocardial perfu sion and evaluation of ventricular wall motion. An ungated perfusion scan p roduced images with millimeter spatial resolution and quality comparable to human images, allowing the visualization of the left and right ventricular myocardium.