Characterization and Quantification of Image Quality in CT Imaging Systems: A Phantom Study

Computed Tomography (CT) is a widely used imaging technique in lung cancer screening programs. To address the problem of exposing potentially healthy patients to ionizing radiation, Iterative Reconstruction (IR) algorithms can be employed. Indeed, traditional Filtered Back Projection reconstruction does not deliver adequate image quality with reduced dose levels. IR instead is prone to preserve diagnostic information and resolution while reducing noise and radiation dose. We characterized image quality for two CT scanners equipped with different iterative algorithms by using a quantitative metric, the detectability index. We compared the dependence of the image quality on the dose and the iterative level when the human visual perception is considered or not in the detectability index definition. It has been found that similar image quality can be obtained by using different scanners and different combinations of dose and iterative levels. This allows us to extrapolate the protocols c orresponding to a lower dose while preserving as much as possible the imaging properties.