SPECT/CT Imaging Acquisition and Reconstruction Protocol

All imaging acquisitions were performed with a SPECT/CT Discovery NM/CT 670 (General Electric [GE] Healthcare), including a BrightSpeed 16 CT scanner and a 3/8-inch NaI(Tl) crystal, according to the acquisition protocol previously described [12 (link)]. Briefly, nuclear medicine images were acquired using a medium-energy general purpose parallel-hole collimator. A 20% energy window centred on the 208 keV photopeak and a 10% scatter correction window centred on 177 keV were applied. NM acquisitions were performed using a body contour option, rotation of 180° per detector, total of 60 projections and 45 s each. For attenuation correction, CT images were acquired (120 kV, automatic mA regulation with a max at 200 mA, noise index at 6.43, slice thickness of 5 mm, rotation time of 0.8 s, pitch 1.375, 512 × 512 pixels matrix), with standard reconstruction.
The application “Preparation for Dosimetry Toolkit” was used for SPECT/CT image reconstruction for both dosimetry approaches. The Ordered Subset Expectation Maximization iterative reconstruction algorithm was used with 6 iterations and 10 subsets, attenuation, scatter, recovery resolution corrections and a Gaussian post-filter of 0.11 cm [12 (link)].