B78-20 Lobar CT-based Deformation Metrics Add Functional Information Beyond GOLD Staging

Rationale

Spirometric classification using GOLD stages is central to COPD assessment, yet patients within the same stage often differ in symptoms and functional status. While CT-based measures of emphysema and airway wall thickness capture structural abnormalities, they do not directly assess regional lung mechanics. By registering inspiratory-expiratory CT scans, lung deformation during ventilation can be quantified using the Jacobian determinant, which reflects regional lung expansion and contraction. This study investigates whether lobar Jacobian deformation metrics provide additional information across spirometric categories.

Methods

We analyzed chest CT scans from 728 COPDGene participants, selected using propensity score matching to balance age, height, sex, and race across spirometric categories (healthy controls, GOLD 0, pRISM, GOLD 1-4). Complete imaging data were available for 676 individuals. Lung lobes were automatically segmented using the deep learning model TotalSegmentator. Inspiratory and expiratory CT scans were non-rigidly registered with the deep learning model uniGradICON to generate voxel-wise deformation fields. From these fields, Jacobian determinants were calculated to quantify regional lung contraction during expiration (lower values = greater contraction). Mean and standard deviation of the Jacobian were calculated for each lobe, and inter-lobar heterogeneity was quantified using the coefficient of variation (CV) across the five lobes. Differences in whole-lung Jacobian and inter-lobar CV across spirometric categories were evaluated using Kruskal-Wallis tests, followed by post hoc Dunn tests for pairwise comparisons.

Results

Regional lung deformation differed across spirometric categories and lobes. Lower Jacobian determinants were seen in healthy controls (0.732) and GOLD 0 (0.749), with progressively higher values across increasing disease severity, reaching 0.887 in GOLD 4. Upper lobes consistently contracted more than lower lobes. Inter-lobar heterogeneity decreased with disease progression (median CV 0.112 in controls vs. 0.062 in GOLD 4), suggesting more uniform deformation in advanced COPD. Kruskal-Wallis tests confirmed significant differences across categories for both whole-lung Jacobian (H = 243.1, p < 1e-48) and inter-lobar CV (H = 90.9, p < 1e-16), with post hoc Dunn tests showing that deformation and heterogeneity metrics distinguished early disease from controls and more advanced stages.

Conclusions

CT-derived Jacobian deformation metrics capture regional ventilation mechanics that vary across spirometric disease categories. Early changes in whole-lung deformation distinguish GOLD 0 from mild COPD, while decreasing inter-lobar heterogeneity characterizes more advanced disease. These findings suggest that regional lung mechanics provide supplemental information to spirometry and may help explain clinical heterogeneity in COPD beyond GOLD staging.

This abstract is funded by: None