Safire algorithm

The Somatom’s standard low-dose CT colonography protocol is optimised for non-contrast acquisitions and consists of four total scans: supine, prone and two topograms. The protocol employs the CARE Dose4D and CARE kV dose optimisation software, with the latter prioritising a higher level of image quality for the supine scan versus the prone scan. Iterative reconstruction is handled by Siemens Healthcare’s SAFIRE algorithm and defaults to level 3 on the noise reduction scale of 1–5, which represents the middle ground between noisy and smoothed images.²⁰ Phantom setup was the same as for the Ingenuity, and tube output was confirmed for the supine and prone sequences.

Iterative reconstruction of the 80 kV raw data was performed using the SAFIRE algorithm (Siemens Healthcare, Forchheim, Germany) at a medium and high setting (I3 and I5) and a soft tissue kernel (I31f). A virtual data set with 120 kV, 70% of which was comprised of the data from the 140 kV tube and 30% of the data from the 80 kV tube, was calculated from the raw data for the two tubes. Virtual 120 kV data was reconstructed using filtered back-projection (FBP) and a soft tissue kernel (B30f). Both image data sets were generated with a slice thickness of 3 mm and an increment of 3 mm.