Performance characterization of a high-purity germanium detector for small-animal SPECT

We present an initial evaluation of a mechanically-cooled, high-purity germanium double-sided strip detector as a potential gamma camera for small-animal SPECT. It is 90 mm in diameter and 10 mm thick with two sets of 16 orthogonal strips that have a 4.75 mm width with a 5 mm pitch. A sub-strip interpolation method is used to bin the data at a pixel size of 0.53mm × 0.53mm, while it is also possible to estimate the depth of interaction based on CFD time differences between the anode and cathode. The system has an energy resolution of 0.92% at 140 keV and an intrinsic efficiency of 55.40% at 122 keV. Simulations suggest that increases in the efficiency should be possible by altering signal processing to include Compton events in which charge is collected on more than one strip. Integral uniformity in the central field of view for strips was found to be less than 1% in a flood-corrected flood while pixel-level uniformity was 2.98%. Due to the excellent energy resolution, the presence of a scattering medium did not greatly alter the FWHM or FWTM of a pinhole projection when compared to an acquisition without a scattering medium. This high-purity germanium system offers many desirable properties for small-animal SPECT.