ECG-gated pinhole SPECT in mice with millimeter spatial resolution

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