Pulmonary Blood Vessels
Detailed segmentation and analysis of the pulmonary circulation are needed for computer-assisted diagnosis or computer-assisted surgery as described in Chap. 4. For example, adjacent pulmonary blood vessel anatomy is an important information to include in the analysis of lung nodules detected on CT. In bronchoscopic navigation, it is important to prevent inserting a biopsy needle into a pulmonary artery branch during transbronchial needle biopsy (TBLB).
Fig. 3.54 Examples of anatomical labeling of bronchi
Because pulmonary blood vessels are depicted as white regions on chest CT images, it is possible to segment lower-order vessels by simple thresholding. However, because of gravitational pull, the side of the lungs that is close to the ground has relatively higher density than that on the upper side. Adaptive thresholding or another more sophisticated approach is necessary.
This method extracts pulmonary blood vessels based on simple thresholding. Because pulmonary blood vessels have CT values of around —500 H.U. or more, it would be possible to extract pulmonary blood vessels by performing a thresholding operation inside the lung area. The lung area is also easily segmented from CT images by simple thresholding and connected component analysis.