Schematic representation of the determination of lung segments by using distance information. The box represents a lung lobe. (Left) The segmental branches of the pulmonary artery (PA) are colored differently. (Right) Each point of the lobe is assigned to the nearest segment branch and the corresponding segment, respectively.
Pulmonary artery branches run in parallel to the bronchial tree branches and segmental broundaries are situated between segmental branches of neighboring segments. Illustrated for the right upper lobe from left to right: Segmental bronchial tree branches, segmental pulmonary artery branches, segmental bronchial tree and segmental pulmonary artery branches, resulting segments computed with the PA-based method.
Workflow diagram of the segment approximation method.
Outline of the lung segment approximation method illustrated by the subdivision of the right upper lobe. From top left to bottom right: Original CT image, lobe segmentation result shown in an axial slice, pulmonary artery segmentation result (view from front), labeled segmental branches of the pulmonary artery of the right upper lobe (view from top-right), lung segment approximation result for the right upper lobe (view from top-right), lung segment approximation results of the complete lung (views from right, front and left).
Illustration of the intersegmental pulmonary veins used as reference data. The figure shows segments S2 (red) and S3 (light red) of the right upper lobe and the pulmonary vein (white). The vein portions running in the intersegmental planes between segments S1 and S2 and between S1 and S3 are marked in orange. The vein parts running within segment S1 are marked in magenta.
Scheme of the lung regions used in the experiments (axial slice view of right lung): (a) complete lung, (b) hilum region, and (c) nonhilum region.
Results of the PA-based method. From left to right: Computed segments in axial, coronal, sagittal slice, and 3D view. From top to bottom: Right upper, right middle, right lower, left upper, and left lower lobe segments.
Results of experiments 1 and 2 on the complete lung regions (measured in mm).
Results of experiments 1 and 2 on nonhilum regions with different hilum region sizes (measured in mm).
Results of experiments 1 and 2 on hilum regions with different hilum region sizes (measured in mm).
Results of Wilcoxon's signed-rank test applied to the differences between the mean deviations between the computed segment boundaries and the reference intersegmental veins achieved by the PA-based method and the BT-based method, respectively.
Analysis of the position of the intersegmental veins identified in the test cases: For each segment, the number of cases with intersegmental veins delimiting the segment and the total number of intersegmental veins delimiting the segment over all cases are given.
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