Pulmonary Fissure Integrity Assessment in Subjects with Severe Emphysema: Evaluation of a Fully Automatic Method

RATIONALE: Pulmonary fissures are important anatomical landmarks in recognizing pulmonary lobar structure and the regional assessment of the extent and distribution of lung disease. Incomplete fissures contribute to collateral ventilation across lobes and detection and quantification of incomplete lobar fissures may have clinical implications for the outcome of resections and bronchoscopic lung volume reduction (BLVR) planning for emphysema patients. The purpose of this study is to evaluate a technique for automatic quantification of fissural completeness from chest computed tomography scans on a database of subjects with severe emphysema. METHODS: From an imaging research database, 96 patients with severe emphysema enrolled in clinical trials for BLVR treatment were identified. Standardized pre-treatment volumetric CT imaging of the thorax was performed at suspended full inspiration with at most 1 mm slice thickness at 120 KV and 80-110 mAs. Fissural completeness for the left major and right major and minor fissures was assessed by visual read and automatic quantification. Visual assessment of fissural completeness was performed by two expert radiologists inspecting all three planes. For visual scoring a dichotomous scale was used to score fissure integrity: complete or partial. A complete fissure was defined as more than 90% intact surface of the fissure and no obvious vessels crossing over. For automatic quantification, the lungs, fissures, and lobes were automatically segmented and the percentage integrity of the fissures was calculated as the percentage of the lobar border defined by a fissure. The continuous integrity score of the automatic method is compared to the dichotomous visual assessments of both readers using ROC analysis, boxplots, and rank sum tests. RESULTS: For all three pulmonary fissures, compared to both readers, boxplot analysis showed that the automatic method gave significantly higher completeness scores (means 91.04%, 93.16%, 93.65% and 90.06%, 88.08%, 93.77%, for the right major, right minor, and left major fissures, for both readers, respectively) for fissures assessed by the readers as complete than for those assessed as partial (means 83.17%, 69.49%, 86.18%, and 82.97%, 70.09%, 85.16% ) (p<0.001). The kappa statistics for the radiologists? agreement were 0.75, 0.59, and 0.74, respectively. The ROC curves for the automatic method compared to each reader for each fissure are provided in Figure 2. CONCLUSION: A completely automatic method for quantification of fissural completeness is able to quantify fissural completeness in a cohort of subjects with severe emphysema comparable to expert radiologists.