Impact of iterative reconstructions on objective and subjective emphysema assessment with computed tomography: a prospective study

Objectives To prospectively evaluate the impact of iterative reconstruction (IR) algorithms on pulmonary emphysema assessment as compared to filtered back projection (FBP). Methods One hundred ten unenhanced chest CT examinations were obtained on two different scanners. Image reconstructions from a single acquisition were done with different levels of IR and compared with FBP on the basis of the emphysema index (EI), lung volume and voxel densities. Objective emphysema assessment was performed with 3D software provided by each manufacturer. Subjective assessment of emphysema was performed as a blinded evaluation. Quantitative and subjective values were compared using repeated ANOVA analysis, Bland-Altman analysis and Kendall’s coefficient of concordance (W). Results Lung volumes are stable on both units, throughout all IR levels ( P ≥ 0.057). EI significantly decreases on both units with the use of any level of IR ( P