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 (αQ-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 highperformance imaging system capable of imaging alpha-emitters in preclinical applications.