Eur Radiol (2012) 22:302–309 crossing from adjacent lobes. The score absent was used when no appreciable fissure could be seen. In all other cases, the fissures were scored as partial. For all 96 CT studies, two radiologists with four and six years’ experience independently scored the completeness of all lobar fissures. For cases where the two radiologists disagreed, a consensus reading was performed with a chest radiologist who had 14 years’ experience. The two radiologists disagreed in 36 out of 288 (12.5%) fissures, out of which 12 were right major fissures, 13 right minor fissures and 11 left major fissures. The kappa between the readers were 0.75, 0.67 and 0.74, for the right major, right minor and left major fissures respectively Automatic fissural completeness quantification The lungs, fissures and lobes were automatically segmented using previously proposed and evaluated methods [8–10]. The lung segmentation was performed using a hybrid method specifically designed to overcome segmentation errors typical in CT studies exhibiting pathological features [8]. The lung segmentation begins with a conventional approach to segmenting the lungs using region-growing and morphology. Segmentation failure was automatically detected based on statistical deviation from a range of volume and shape measurements. To CT studies with segmentation errors, an advanced, multi-atlas-based algo- rithm using non-rigid registration was applied. 305 Fissure detection was based on pattern classification using image derivatives, image gradient and Hessian features. The pattern classification was trained based on manually identified examples of fissure and non-fissure voxels, as described in van Rikxoort et al. [9]. For this study, the fissure detection method was trained using manually segmented fissures in the 20 CT studies set aside for development. Given the fissures detected, the lobe borders were automat- ically segmented by fitting an atlas with complete fissures (see van Rikxoort et al. [10]). As a result, the lobe borders are derived, even when the fissures are incomplete. The completeness of a pulmonary fissure is determined from the segmentations of the lobe and fissure by assigning each point on the detected fissure to the closest point on the lobe border; voxels on the lobe border not assigned to a fissure voxel are considered to be non-fissure and therefore incomplete. The percentage of lobar border voxels identified as complete quantifies the completeness of the fissure. The result of the automatic fissural completeness quantification is visually displayed as a colour-coded lobar boundary. The procedure of fissural completeness calculation is illustrated in Fig. 1. Statistical analysis Descriptive statistics on fissural completeness for both the visual scoring and the automatic quantification are provid- ed. Box-plots are provided for the automatic score stratified by the different visual categories for the consensus read. Fig. 3 Sets of 4 coronal slices from 4 different CT studies and the corresponding output of the automatic fissural completeness quanti- fication method. Voxels in yellow indicate fissure voxels, voxels in red indicate a lobar boundary without a fissure. a Example of a CT study for which all lobar fissures are complete. In (b) an example of an incomplete right minor fissure is shown. c and d Examples of incomplete major fissure(s)