Automated extraction of aorta and pulmonary artery in mediastinum from 3D chest X-ray CT images without contrast medium

This paper proposes a method for automated extraction of the aorta and pulmonary artery (PA) in the mediastinum of the chest from uncontrasted chest X-ray CT images. Since the aorta and PA areas show low intensity contrast in the mediastinum, it is difficult to extract those areas by a procedure based on CT values. The proposed method employs a model fitting technique to use shape features of blood vessels for extraction. First, edge voxels are detected based on the standard deviation of CT values. A likelihood image, which shows the degree of "likelihood" on medial axes of vessels, are calculated by applying the Euclidean distance transformation to non-edge voxels. Second, the medial axis of each vessel is obtained by fitting the model. This is done by referring the likelihood image. Finally, the aorta and PA areas are recovered from the medial axes by executing the reverse Euclidean distance transformation. We applied the proposed method to seven cases of uncontrasted chest X-ray CT images and evaluated the results by calculating the coincidence index computed from the extracted regions and the regions manually traced. Experimental results showed that the extracted aorta and the PA areas coincides with manually input. regions with the coincidence indexes values 90% and 80-90%, respectively.