Reduced-dose chest CT with 3D automatic exposure control vs. standard chest CT: Quantitative assessment of emphysematous changes in smokers’ lung parenchyma

Abstract Objectives To determine the capability of reduced-dose chest CT with three-dimensional (3D) automatic exposure control (AEC) on quantitative assessment of emphysematous change in smoker’ lung parenchyma, compared to standard chest CT. Methods Twenty consecutive smoker patients (mean age 62.8 years) underwent CT examinations using a standard protocol (150 mAs) and a protocol with 3D-AEC. In this study, the targeted standard deviations number was set to 160. For quantitative assessment of emphysematous change in lung parenchyma in each subject using the standard protocol, a percentage of voxels less than −950 HU in the lung (%LAA −950 ) was calculated. The 3D-AEC protocol's %LAA was computed from of voxel percentages under selected threshold CT value. The differences of radiation doses between these two protocols were evaluated, and %LAAs −950 was compared with the 3D-AEC protocol %LAAs. Results Mean dose length products were 780.2 ± 145.5 mGy cm (standard protocol), and 192.0 ± 95.9 (3D-AEC protocol). There was significant difference between them (paired Student's t test, p t test, p  = 0.32) between %LAAs −950 and 3D-AEC protocol %LAAs. In adopting the feasible threshold CT values of the 3D-AEC protocol, the 3D-AEC protocol %LAAs were significantly correlated with %LAAs −950 ( r  = 0.98, p Conclusions Changing threshold CT values demonstrated that reduced-dose chest CT with 3D-AEC can substitute for the standard protocol in assessments of emphysematous change in smoker’ lung parenchyma.