Visual score and quantitative CT indices in pulmonary fibrosis: Relationship with physiologic impairment

The aim of this study was to assess the accuracy of some computed tomography (CT) quantitative indices (histogram features, ranges of density and one novel volumetric index) in the discrimination between normals and patients affected by lung fibrosis, and to compare their morphologic-functional relationship with the visual score one.

We analysed thin-section CTs and pulmonary function tests (PFTs) of six healthy subjects and 31 patients affected by lung fibrosis, including 17 with a usual interstitial pneumonia pattern (UIP group), and 14 with a predominant pattern of ground-glass opacities without honeycombing (non-UIP group). Presence and extent of various CT findings were assessed by the visual score as well as by CT computer indices.

Together with the histogram features, fibrosis ratio (defined as the ratio of nonfibrotic CT lung volume divided by total CT lung volume) contributed to objectively differentiate fibrotic lungs from normal lungs. The range of density 700 to 400 HU showed the greatest degree of correlation with physiologic abnormality in the non-UIP group. In the UIP group, the lone visual score provided prediction of functional impairment.

The visual score is still the main radiological method of quantifying the extent of abnormalities in patients with UIP, whilst the range of density 700 to 400 HU can be helpfully applied in a predominant pattern of ground-glass and reticular opacities without honeycombing.