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      CT-derived Biomechanical Metrics Improve Agreement Between Spirometry and Emphysema

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          Abstract

          <div class="section"> <a class="named-anchor" id="S1"> <!-- named anchor --> </a> <h5 class="section-title" id="d4972857e205">Rationale and Objectives</h5> <p id="P2">Many COPD patients have marked discordance between FEV <sub>1</sub> and degree of emphysema on CT. Biomechanical differences between these patients have not been studied. We aimed to identify reasons for the discordance between CT and spirometry in some patients with COPD. </p> </div><div class="section"> <a class="named-anchor" id="S2"> <!-- named anchor --> </a> <h5 class="section-title" id="d4972857e213">Materials and Methods</h5> <p id="P3">Subjects with GOLD stage I–IV from a large multicenter study (COPDGene) were arranged by percentiles of %predicted FEV <sub>1</sub> and emphysema on CT. Three categories were created using differences in percentiles: Cat <sub>spir</sub> with predominant airflow obstruction/minimal emphysema, Cat <sub>CT</sub> with predominant emphysema/minimal airflow obstruction, and Cat <sub>matched</sub> with matched FEV <sub>1</sub> and emphysema. Image registration was used to derive Jacobian determinants, a measure of lung elasticity, anisotropy and strain tensors, to assess biomechanical differences between groups. Regression models were created with the above categories as outcome variable, adjusting for demographics, scanner type, quantitative CT-derived emphysema, gas trapping, and airway thickness (Model 1), and after adding biomechanical CT metrics (Model 2). </p> </div><div class="section"> <a class="named-anchor" id="S3"> <!-- named anchor --> </a> <h5 class="section-title" id="d4972857e233">Results</h5> <p id="P4">Jacobian determinants, anisotropy and strain tensors were strongly associated with FEV <sub>1</sub>. With Cat <sub>matched</sub> as control, Model 2 predicted Cat <sub>spir</sub> and Cat <sub>CT</sub> better than Model 1 (Akaike Information Criterion, AIC 255.8 vs. 320.8). In addition to demographics, the strongest independent predictors of FEV <sub>1</sub> were Jacobian mean (β= 1.60,95%CI = 1.16 to 1.98; p&lt;0.001), coefficient of variation (CV) of Jacobian (β= 1.45,95%CI = 0.86 to 2.03; p&lt;0.001) and CV strain (β= 1.82,95%CI = 0.68 to 2.95; p = 0.001). CVs of Jacobian and strain are both potential markers of biomechanical lung heterogeneity. </p> </div><div class="section"> <a class="named-anchor" id="S4"> <!-- named anchor --> </a> <h5 class="section-title" id="d4972857e253">Conclusions</h5> <p id="P5">CT-derived measures of lung mechanics improve the link between quantitative CT and spirometry, offering the potential for new insights into the linkage between regional parenchymal destruction and global decrement in lung function in COPD patients. </p> </div>

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          Author and article information

          Journal
          Academic Radiology
          Academic Radiology
          Elsevier BV
          10766332
          October 2016
          October 2016
          : 23
          : 10
          : 1255-1263
          Article
          10.1016/j.acra.2016.02.002
          5026854
          27055745
          e323452c-06ee-4263-90a8-0037d27b5e06
          © 2016

          https://www.elsevier.com/tdm/userlicense/1.0/

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