Idiopathic Pulmonary Fibrosis: Data-driven Textural Analysis of Extent of Fibrosis at Baseline and 15-Month Follow-up

Abstract

Purpose To evaluate associations between pulmonary function and both quantitative analysis and visual assessment of thin-section computed tomography (CT) images at baseline and at 15-month follow-up in subjects with idiopathic pulmonary fibrosis (IPF). Materials and Methods This retrospective analysis of preexisting anonymized data, collected prospectively between 2007 and 2013 in a HIPAA-compliant study, was exempt from additional institutional review board approval. The extent of lung fibrosis at baseline inspiratory chest CT in 280 subjects enrolled in the IPF Network was evaluated. Visual analysis was performed by using a semiquantitative scoring system. Computer-based quantitative analysis included CT histogram-based measurements and a data-driven textural analysis (DTA). Follow-up CT images in 72 of these subjects were also analyzed. Univariate comparisons were performed by using Spearman rank correlation. Multivariate and longitudinal analyses were performed by using a linear mixed model approach, in which models were compared by using asymptotic χ² tests. Results At baseline, all CT-derived measures showed moderate significant correlation (P < .001) with pulmonary function. At follow-up CT, changes in DTA scores showed significant correlation with changes in both forced vital capacity percentage predicted (ρ = -0.41, P < .001) and diffusing capacity for carbon monoxide percentage predicted (ρ = -0.40, P < .001). Asymptotic χ² tests showed that inclusion of DTA score significantly improved fit of both baseline and longitudinal linear mixed models in the prediction of pulmonary function (P < .001 for both). Conclusion When compared with semiquantitative visual assessment and CT histogram-based measurements, DTA score provides additional information that can be used to predict diminished function. Automatic quantification of lung fibrosis at CT yields an index of severity that correlates with visual assessment and functional change in subjects with IPF. ^© RSNA, 2017.

A, Axial baseline unenhanced CT image in a 60-year-old man. B, Areas of fibrosis identified with DTA are indicated (red ●). Baseline DTA fibrosis score was 22.3%, average visual extent of fibrosis as assessed by three readers (D.L., E.v.B., E.K.) was 1.67, baseline FVC percentage predicted was 53.15, and DLco percentage predicted was 36.1. C, Similar axial unenhanced CT image in the same subject at 18.2-month follow-up. D, DTA fibrosis score was 40.6% at follow-up, average visual extent of fibrosis (D.L., E.v.B., and E.K.) was 3.67, with all three readers scoring the follow-up image as slightly worse. Follow-up FVC percentage predicted was 44.4 and DLco percentage predicted was 30.5.