Radiation dose reduction in hepatic multidetector computed tomography with a novel adaptive noise reduction filter

Abstract

The aim of this study was to optimize a novel adaptive noise reduction filter based on patient body weight and to investigate its utility for improving the image quality of low-dose hepatic computed tomography (CT) scans. The tube current-time product was changed from 140 to 180 and from 60 to 100 mAs at standard- and low-dose CT, respectively, based on the body weights of 45 patients. Unenhanced and two-phase contrast-enhanced helical scans were obtained at the standard dose during the hepatic arterial and equilibrium phases. During the equilibrium phase, we obtained low-dose scans of the liver immediately after standard-dose scans. The low-dose CT images were postprocessed with the filter. Two radiologists visually evaluated artifacts in the liver parenchyma and its graininess, the sharpness of the liver contour, tumor conspicuity, homogeneity of the enhancement of the portal vein, and overall image quality. There was no statistically significant difference between standard and filtered low-dose images with respect to artifacts in the liver, the graininess of the liver parenchyma, tumor conspicuity, homogeneity of enhancement of the portal vein, or overall image quality. The adaptive noise reduction filter effectively reduced image noise. We confirmed the effectiveness of the filter by examining clinical hepatic images obtained at low-dose CT.