Fig. 4

Sphere-to-background ratios for the NEMA IQ phantom for the 3D CZT Veriton SPECT/CT images in blue, and for the conventional Symbia SPECT/CT images in red (with the true sphere-to-background ratio equal to 12.1) The high-count (HC) images are depicted by ’o’ and the low-count (LC) images by ’x’. The increasing number of updates are 10, 20, 50, 100 and 200 for the 3D CZT Veriton SPECT reconstructions and 16, 64, 256 and 384 for the Symbia reconstructions. Data points were subsequently connected by the grey dotted line with black circles indicating the chosen clinical protocol for both systems