Comparison of Advanced Iterative Reconstruction Methods for SPECT/CT

Abstract

On three SPECT/CT systems, manufactured by General Electrics, Siemens and Philips, all of them installed recently, a SPECT acquisition (360°, 6°/step, 40sec./frame) of a resolution and the NEMA NU2-2001 image quality phantom was performed. Reconstructions were done using Evolution for bone (GE), Flash3D (Siemens) and Astonish (Philips). The reconstructed slices were either analyzed directly or after additional post-filtering according to the manufacturers recommendation using in-house developed analysis tools. FWHM was 13.1/9.5 mm (filter/no filter) for GE, 11.4/9.0 for Siemens and 16.0/10.6 mm for Philips. If the OSEM/MLEM reconstruction is taken as gold standard we found a relative improvement in resolution of 9.0/34% (filter/no filter) for GE, 0/21% for Siemens and 0/29% for Philips. FWTM was 22.4/19.9 mm (filter/no filter) for GE, 20.9/17 mm for Siemens and 32.0/22 mm for Philips. Corresponding reference values were higher by 21.0/29% (filter/no filter) for GE, 0/18% for Siemens, 0/24% for Philips. We measured approximately the same percent contrast applying Evolution/Flash3D and Astonish and OSEM/MLEM for the two largest spheres (37 and 28mm) but found a significant improvement if the size of the spheres is decreased. Spatial resolution and percent contrast significantly improves using the nowadayscommercial available advanced reconstruction technology in a realistic clinical setting. Great care must be taken to avoid unnecessary filtering which might be the default setting in some protocols.