Performance Evaluation of the Discovery NM/CT 670 CZT

Objectives: The Discovery NM/CT 670 CZT is the first commercially available cadmium-zinc-telluride (CZT)-based whole-body SPECT/CT. The aim of this study was to evaluate the performance of this SPECT system using phantoms and 99mTc-sources. Methods : Energy resolution, system sensitivity, uniformity, spatial resolution, count rate characteristics, and count linearity were evaluated using wide-energy high-resolution (WEHR) collimators, which were exclusively designed for this CZT camera. A 99mTc flood source was used for measurements of energy resolution, system sensitivity, uniformity of planar images, and count rate characteristics. Spatial resolution was evaluated using a 99mTc line source. A JS-10 SPECT phantom was used for assessment of count linearity. Results : The system achieved the energy resolution of 6.18 % in full-width at half maximum (FWHM) at 140 keV. System sensitivity was 78 cps/MBq at 5 cm distance from the source. The integral uniformity of planar image was 2-3%. Planar spatial resolution was 5 mm in FWHM at 2 cm distance from the source, whereas SPECT spatial resolution was 3-4 mm with iterative reconstruction and resolution recovery function at 10 cm of rotation radius. Count rate characteristics were excellent up to 50,000 cps. Finally, there was excellent linearity between 99mTc concentration and measured counts. Conclusion : The results showed that the Discovery NM/CT 670 CZT has good overall performance with high energy resolution, spatial resolution, and excellent count rate characteristics, and should be suitable for clinical use.