For each protocol, you can define and mark extra points along the vessel to help segment the vessel between the start and end points. You can enter as many extra points as required.
Press Shift and click the reference image to mark the point. This point will have the same name as the currently marked line, meaning the one that is checked in the dialog box.
For tracing a path along the aorta and iliac arteries, press Shift and scroll down to mark additional extra points, until you have finished marking the extra points for a specific section of the vessel. When you release the Shift key, the next row (point) is selected (ready for marking) in the Aorta Protocol dialog box.
NOTE: All extra points marked between two named points using the Aorta Protocol will have the same name as the named point preceding the extra points.
To delete the last defined extra point:
Click Delete Last Point 
.
To delete all extra points:
Uncheck the point check box in the protocol dialog box.
All extra points between the last predefined point and the unchecked point are deleted.
See these topics:
Defining and Marking Occlusions