Fig. 2.

Image segmentation process. a,b Screenshot from ITK-SNAP-Software (http://www.itksnap.org) Region growing as part of segmentation. a Example of segmentation via region growth (aorta). Select the region of interest for semi-automatic active contour segmentation and laying down the red dots to define where the region of interest is. b Activating the algorithm causes the dots to expand into the region of interest. c Screenshot from Mimics-Software as an example of thresholding and manual editing. d The histogram window on the bottom right-hand corner is the graph where thresholding is usually set