Noise assessment across two generations of iterative reconstruction algorithms of three manufacturers using bone reconstruction kernel

PurposeTo compare the noise-magnitude and noise-texture obtained using strong kernel across two generations of iterative reconstruction (IR) algorithms proposed by three manufacturers.Materials and methodsFive computed tomography (CT) systems equipped with two generations of IR algorithm (hybrid/statistical IR H/SIR] or full/partial model-based IR MBIR]) were compared. Acquisitions on Catphan 600 phantom were performed at 120 kV and three dose levels (CTDI_vol: 3, 7 and 12mGy). Raw data were reconstructed using standard “bone” kernel for filtered back projection and one iterative level of two generations of IR algorithms. Contrast-to-noise ratio (CNR) was computed using three regions of interest placed semi-automatically: two placed in the low-density polyethylene and Teflon inserts and another placed on the solid water. Noise power spectrum (NPS) was computed to assess the NPS-peak and noise-texture.ResultsCNR was significantly greater in MBIR compared to H/SIR algorithms for all CT systems (P < 0.01). CNR were improved on average from H/SIR to MBIR of 36 ± 14% SD] (range: 24–57%) for GE-Healthcare, 109 ± 19 SD] % (range: 89–139%) for Philips Healthcare and 42 ± 5 SD] % (range: 36–47%) for Siemens Healthineers. The mean NPS peak decreased from H/SIR to MBIR by ?41 ± 6 SD] % (range: ?47–?35%) for GE Healthcare, ?79 ± 3 SD] % (range: ?82–?76%) for Philips Healthcare and ?52 ± 2 SD] % (range: ?54–?51%) for Siemens Healthineers systems. NPS spatial frequencies were greater with MBIR than with H/SIR for Philips Healthcare (20 ± 2 SD] %; range: 19–22%) and for Siemens Healthineers (9 ± 5 SD] %; range: 4–14%) but lower for GE Healthcare (?17 ± 3 SD] %; range: ?14–?20%).ConclusionUsing bone kernel with recent MBIR algorithms reduces the noise-magnitude for all CT systems assessed. Noise texture shifted towards high frequency for Siemens Healthineers and Philips Healthcare but the opposite for GE Healthcare.