title: Toward Understanding the Size Dependence of Shape Features for Predicting Spiculation in Lung Nodules for Computer-Aided Diagnosis.
abstract: We analyze the importance of shape features for predicting spiculation ratings assigned by radiologists to lung nodules in computed tomography (CT) scans. Using the Lung Image Database Consortium (LIDC) data and classification models based on decision trees, we demonstrate that the importance of several shape features increases disproportionately relative to other image features with increasing size of the nodule. Our shaped-based classification results show an area under the receiver operating characteristic (ROC) curve of 0.65 when classifying spiculation for small nodules and an area of 0.91 for large nodules, resulting in a 26% difference in classification performance using shape features. An analysis of the results illustrates that this change in performance is driven by features that measure boundary complexity, which perform well for large nodules but perform relatively poorly and do no better than other features for small nodules. For large nodules, the roughness of the segmented boundary maps well to the semantic concept of spiculation. For small nodules, measuring directly the complexity of hard segmentations does not yield good results for predicting spiculation due to limits imposed by spatial resolution and the uncertainty in boundary location. Therefore, a wider range of features, including shape, texture, and intensity features, are needed to predict spiculation ratings for small nodules. A further implication is that the efficacy of shape features for a particular classifier used to create computer-aided diagnosis systems depends on the distribution of nodule sizes in the training and testing sets, which may not be consistent across different research studies.
authors.affiliation: School of Computing, DePaul University, 243 S. Wabash Avenue, Chicago, IL, 60604, USA. ron.niehaus@live.com.
authors.forename: Ron
authors.initials: R
authors.lastname: Niehaus
authors.affiliation: School of Computing, DePaul University, 243 S. Wabash Avenue, Chicago, IL, 60604, USA.
authors.forename: Daniela Stan
authors.initials: DS
authors.lastname: Raicu
authors.affiliation: School of Computing, DePaul University, 243 S. Wabash Avenue, Chicago, IL, 60604, USA.
authors.forename: Jacob
authors.initials: J
authors.lastname: Furst
authors.affiliation: Department of Radiology, University of Chicago, Chicago, IL, USA.
authors.forename: Samuel
authors.initials: S
authors.lastname: Armato
mesh_terms: D006801:Humans; D008168:Lung / Q000000981:diagnostic imaging; D008175:Lung Neoplasms / Q000000981:diagnostic imaging*; D012372:ROC Curve; D011857:Radiographic Image Interpretation, Computer-Assisted / Q000379:methods*; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D003074:Solitary Pulmonary Nodule / Q000000981:diagnostic imaging*; D014057:Tomography, X-Ray Computed / Q000379:methods*
keywords: Biomedical image analysis; Computed tomography; Computer analysis; Computer-aided diagnosis (CAD); Decision support; Decision trees; Diagnostic imaging; Image interpretation; LIDC