Automatic Fissural Integrity Quantification from Chest CT Predicts Lobar Atelectasis in Endobronchial Treatment

RATIONALE Patients with emphysema are investigated for minimally invasive occlusive endobronchial treatment as an alternative to lung volume reduction surgery (LVRS). Presence of collateral flow through incomplete pulmonary fissure may affect the treatment outcome. Previous research has shown that visual fissure integrity score is associated with lobar collapse. The purpose of this study is to evaluate if an automatic quantitative fissural integrity score from chest CT scans is predictive of achieving lobe volume reduction in patients with severe emphysema treated with minimally invasive treatment. METHODS Baseline and post treatment follow up CT scans from 18 subjects treated with occlusive endobronchial treatment were selected from an anonymized image database. CT imaging of the lung was performed at suspended total lung capacity with 1.25 mm slice thickness, 1mm slice spacing, at 120 KV and 90 mAs. The target lobe for lobar volume reduction was selected as the lobe with the most severe emphysema. Quantification of lobar volumes was performed using in-house developed software that segments the lungs and lobes. The differences between lobar volumes at the baseline and follow up were calculated. In the baseline scans, fissures were automatically segmented and the fissural integrity was quantified as the percentage of the lobar border defined by a fissure. The association between automatically computed fissure integrity percentage at baseline and lobar volume reduction at follow up was assessed using spearman rank test. The odds of complete lobar collapse (volume change of more than 85%) in subjects with complete fissures (integrity percentage more than 90%) was assessed using logistic model. RESULTS The correlation between fissure integrity percentage and percentage lobar collapse was 0.53 (p=0.023). The odds ratio of complete lobar collapse was 2.4 times higher for subjects with complete fissure than with incomplete fissure (p=0.035). CONCLUSION An automated system to both detect and assess fissure integrity correlated with lobar volume reduction post endoluminal occlusion techniques. Advantages of automatic fissural completeness quantification over visual assessment are robustness, precision, and time consumption.