Quantitative performance of a 3D CZT and conventional SPECT/CT for Tb-161 imaging

PURPOSE: This study aimed to assess the imaging performance of a 3D CZT SPECT/CT system for Tb-161 and compare its quantitative accuracy and image quality with those of a conventional [NaI(Tl)]-based SPECT/CT system. METHODS: A NEMA Image Quality (IQ) phantom was scanned with a 3D CZT SPECT/CT (Veriton, Spectrum Dynamics) for 8 min per bed position and with a conventional SPECT/CT (Symbia T16, by Siemens) for 16 min per bed position. The 3D CZT SPECT acquisition time was virtually shortened by reparsing the listmode data. The NEMA IQ phantom was scanned with a cold background and with a sphere-to-background ratio (SBR) of 20:1 and 10:1, with 0.71 MBq/mL in the spheres. Clinical reconstruction protocols were chosen by maximizing the SBR (for the four largest spheres) while minimizing the background noise. RESULTS: The optimal SBR-to-noise trade-off was achieved at 48 updates for the Symbia and 50 updates for the Veriton. The Veriton exhibited a 20% and 34% higher SBR with a 19% and 10% lower CoV compared to the Symbia for the 10:1 and 20:1 spheres to background ratios, respectively. The calibration factors were determined as 15.17 and 4.8 [Formula: see text] cps/MBq for the Symbia and Veriton, respectively. Reducing the scan time had minimal effect on SBR, but a twofold count reduction increased background noise by 11%. CONCLUSION: Quantitative Tb-161 SPECT imaging can be performed using both a conventional and a 3D CZT SPECT/CT. Given its higher sensitivity, the 3D CZT system is preferred, as it achieved better image quality with an 8-min acquisition compared to a conventional system with a 16-min acquisition.