Abstract Rationale Expiration-based biomechanical metrics derived from high-resolution computed tomography (HRCT), such as gas trapping and the Jacobian determinant, characterize abnormalities in local lung expansion and contraction in patients with COPD. These measures are associated with respiratory morbidity and mortality but are limited by their global nature, lacking regional specificity. Endobronchial valve (EBV) therapy offers a minimally invasive alternative to lung volume reduction surgery for emphysema, where HRCT is essential for identifying emphysematous heterogeneity and fissure integrity. Recently, a lung elasticity metric derived from paired inspiration and expiration HRCT scans has been introduced to quantify localized biomechanical function. This study aimed (1) to evaluate lung elasticity as a functional imaging metric and (2) to assess its relationship with structural emphysema severity. Methods The study included 93 subjects who underwent EBV treatment between 2004 and 2023 with available CT baseline and follow-up HRCT imaging (mean interval: 8 months); 57 had paired inspiration-expiration scans. Quantitative CT features included emphysema score (relative area RA below -950 HU) and lung elasticity, expressed as Young’s modulus (kPa). Young’s modulus was categorized into three ranges: 1-3 kPa, 4-8 kPa, and 8 kPa. Values of 4-8 kPa represent normal elasticity, 1-3 kPa indicate reduced recoil capacity, and 8 kPa reflect increased tissue stiffness. The elasticity analysis pipeline involved: (1) image registration of inspiration to expiration scans, (2) computation of deformation vector fields, (3) derivation of Jacobian determinants, (4) conversion to elasticity maps by optimizing the elastic and shear modulus forces, and (5) quantification of elasticity by lobe using RA of Young’s modulus within 1-3 kPa. Analysis was performed by target (i.e. EBV treated lobe) and ipsilateral lobe as well. Spearman rank correlations were performed to test associations. Results Lung elasticity metrics were successfully computed for 50 subjects with paired scans. Median (±IQR) Young’s modulus RA within 1-3kPa was 91.7% (±3.7) in the target lobe and 85.6% (±9.3) in the ipsilateral lobe. Median (±IQR) RA-950HU values were 47.4% (±24.4) and 28.7% (±15.2) for target and ipsilateral lobes, respectively. Significant associations were found between Young’s modulus within 1-3kPa and RA-950HU in both target and ipsilateral lobe (ρ = 0.405 and p = 0.0038; ρ = 0.39 and p = 0.0051, respectively). Conclusions High RA in Young’s modulus 1-3kPa confirms the choice of target lobe. Lobar lung elasticity may provide complementary functional information to structural metrics. Young’s modulus demonstrates potential as a localized functional metric warranting further study. This abstract is funded by: NIH
Kim et al. (Fri,) studied this question.