Symbia t16 spect ct system

Conventional SPECT/CT imaging was performed with a dual-head Siemens Symbia T16 SPECT/CT system, equipped with medium-energy general-purpose parallel-hole collimators. Acquisition parameters of the CT scan were set to 130 kV, 30 mAs, and $0.97\times 0.97\times 5{\text{mm}}^3$ voxel size while the SPECT scanning protocol followed the protocol described by Marin et al. [8 (link)] with the following parameters: a $128\times 128$ matrix, voxel size of 4.79 mm, 32 views with 30 s per view, and an energy window centered at the 208 keV photopeak (with a 20% width) combined with a lower scatter window (with a 10% width). The projection data were decay and scatter corrected and reconstructed using Ordered Subsets Expectation Maximization (OSEM) [9 (link)]. To optimize the reconstruction protocol such that sphere-to-background ratios were as close as possible to the true ratio while keeping the noise level as low as possible, the number of iterations and subsets were gradually increased (4i4s, 8i8s, 16i16s and 24i16s) with 16 the highest possible number of subsets. In addition, default post-smoothing was performed with a Gaussian filter of 1 mm Full width half maximum (FWHM), with additional filtering being considered to further reduce the noise if necessary.