Effects of Model-Based Iterative Reconstruction in Low-Dose Paranasal Computed Tomography: A Comparison with Filtered Back Projection and Hybrid Iterative Reconstruction

Iterative reconstruction (IR) improves image quality compared with filtered back projection (FBP). This study investigated the usefulness of model-based IR (forward-projected model-based iterative reconstruction solution [FIRST]) in comparison with FBP and hybrid IR (adaptive iterative dose reduction three-dimensional process-ing [AIDR 3D]) in low-dose paranasal CT. Twenty-four patients with paranasal sinusitis who underwent stan-dard-dose CT (120 kV) and low-dose CT (100 kV) scanning before and after medical treatment were enrolled. Standard-dose CT scans were reconstructed with FBP (FBP120), and low-dose CT scans with FBP (FBP100), AIDR 3D, and FIRST. The signal-to-noise ratio (SNR) and contrast-to-noise ratio (CNR) in three anatomical structures and effective doses were compared using Mann-Whitney U test. Two radiologists independently evaluated the visibility of 16 anatomical structures, overall image quality, and artifacts. Effective doses in low -dose CT were significantly reduced compared with those in standard-dose CT (0.24 vs 0.43 mSv, p < 0.001). FIRST achieved significantly higher SNR (p < 0.01, respectively) and CNR (p < 0.001, respectively) of evaluated structures and significant improvement in overall image quality (p < 0.001), artifacts (p < 0.001), and visibility related to muscles (p < 0.05) compared to FBP120, FBP100, and AIDR 3D. FIRST allowed radiation-dose reduc-tion, while maintaining objective and subjective image quality in low-dose paranasal CT.