Reducing Radiation Dose at Chest CT: Comparison Among Model-based Type Iterative Reconstruction, Hybrid Iterative Reconstruction, and Filtered Back Projection

Abstract

The study aimed to evaluate the performances of two iterative reconstruction (IR) algorithms and of filtered back projection (FBP) when using reduced-dose chest computed tomography (RDCT) compared to standard-of-care CT. An institutional review board approval was obtained. Thirty-six patients with hematologic malignancies referred for a control chest CT of a known lung disease were prospectively enrolled. Patients underwent standard-of-care scan reconstructed with hybrid IR, followed by an RDCT reconstructed with FBP, hybrid IR, and iterative model reconstruction. Objective and subjective quality measurements, lesion detectability, and evolution assessment on RDCT were recorded. For RDCT, the CTDIvol (volumetric computed tomography dose index) was 0.43 mGy⋅cm for all patients, and the median [interquartile range] effective dose was 0.22 mSv [0.22-0.24]; corresponding measurements for standard-of-care scan were 3.4 mGy [3.1-3.9] and 1.8 mSv [1.6-2.0]. Noise significantly decreased from FBP to hybrid IR and from hybrid IR to iterative model reconstruction on RDCT, whereas lesion conspicuity and diagnostic confidence increased. Accurate evolution assessment was obtained in all cases with IR. Emphysema identification was higher with iterative model reconstruction. Although iterative model reconstruction offered better diagnostic confidence and emphysema detection, both IR algorithms allowed an accurate evolution assessment with an effective dose of 0.22 mSv.