The Alpha-SPECT-Mini: A Small-Animal SPECT System Based on Hyperspectral Compound-Eye Gamma Cameras

There is a rising interest in Single Photon Emission Computed Tomography (SPECT) imaging systems with improved energy resolution to facilitate multi-functional molecular imaging applications, such as alpha-emitter radiopharmaceutical therapy (α-RPT). In this paper, we report the design and evaluation of the Alpha-SPECT-Mini system that offers an ultrahigh energy resolution and high sensitivity for small animal studies. The Alpha-SPECT-Mini system is constructed based on small-pixel CdTe detectors that offers sub-1keV Full-Width-Half-Maximum (FWHM) energy resolution for single pixel events and an average ~2.5keV energy resolution at 122 keV and ~3.5 keV at 218 keV over 153600 pixels in the system. This allows to easily identify X- and gamma-ray contributions in densely populated spectra, such as from the Ac-225 decay chain. The system uses a 96-loft-hole collimator and six stationary detection panels in a full ring geometry. Finally, the system performance is demonstrated using Tc-99m- and Ac-225-filled resolution and image quality (IQ) phantoms. We have experimentally demonstrated that the Alpha-SPECT-Mini is a high-performance imaging system capable of imaging alpha-emitters in preclinical applications.