Eur Radiol (2012) 22:302–309 Table 1 Subject baseline characteristics for all 96 subjects Variable Male BMI DLCO (mL/min/mmHg) DLCO (% predicted) FVC (L) FEV1 (L) FEV1 (%predicted) CT lung volume TLC (L) Voxels below −950 HU (%) Absolute (Mean±SD) 48 23.3 (±3.9) 6.3 (±3.7) 30.4 (±10.1) 2.3 (±0.7) 0.65 (±0.71) 23.2 (±0.71) 6.9 (±1.5) 43.3 (±10.1) BMI body mass index; DLCO diffusing capacity of the lung for carbon monoxide; FVC forced vital capacity; FEV1 forced expiratory volume in 1 second; CT computed tomography; TLC total lung capacity; RV residual volume; HU Hounsfield units; L litres. the pulmonary lobar structure and the regional assessment of the extent and distribution of lung disease. Lobar fissures are often incomplete, leading to parenchymal fusion between the lobes [1–3]. The relationship between fissure incompleteness and collateral flow across adjacent lobes is unknown. Recent treatment strategies aimed at causing regional volume loss by occluding or disrupting airflow to diseased segments of the lung have resulted in a need to better understand the anatomy and functional consequence of fissure completeness. In a recent rando- mised study of bronchoscopic lung volume reduction (BLVR) treatment for emphysema patients it was shown that radiographic evidence of fissure completeness was, in fact, associated with a better response to treatment [4]. Incomplete pulmonary fissures and their variations based on autopsy data were reported for the first time by Medlar [5] in 1947. Subsequently, several papers have 303 been published reporting the percentages of incomplete fissures observed in computed tomography (CT) data by visual scoring [1–3, 6, 7]. The present study advances the existing literature in two ways. First, a method for quantitatively assessing fissural completeness is proposed, and second, the extent to which fissures are classified as complete versus incomplete in a group of patients with severe emphysema is evaluated, whereas previous studies focused on disease-free lung parenchyma. The purpose of this study is to evaluate the proposed automatic fissural completeness quantification of a database of emphysema patients by comparison with a three reader consensus. Materials and methods Data collection From an anonymised image database of patients with emphysema collected in the setting of clinical trials, 1495 CT studies were identified with severe homogeneous emphysema (defined as having an emphysema score at −910 Hounsfield Units (HU) of at least 25% in each lobe, and a difference in emphysema score for the different lobes of less than 25%). A subset of 116 patient CT studies were selected if they met the criteria of having near-isotropic voxel size and slice spacing (axial resolu- tion between 0.6 and 0.8 mm and slice spacing of at most 1 mm). 20 cases were used for developing the computer system and another 96 were read for testing. Table 1 provides descriptive baseline statistics for the 96 CT studies used in this paper. The patient characteristics and emphy- sema severity were the same for the development set and the reading set. Image acquisition protocols were stand- ardised for specific CT systems at each site to maintain a Fig. 1 Illustration of the calculation of the percentage of the fissure’s completeness. The left frame shows an original coronal slice of a right lung. In the second frame the automatically found (incomplete) fissure is shown, followed by the automatically determined lobar border in the third frame. The last frame shows the colour-coded lobar boundary that is the output of the system. Voxels in yellow indicate fissure voxels, voxels in red indicate a lobar boundary without a fissure. The percentage complete is now simply calculated as the number of yellow voxels divided by the total number of voxels on the lobar boundary. Note that this image is a 2D slice, but the calculation of fissural completeness is performed in 3D