Figure 4a.

Ontology-assisted image navigation. (a) Pop-up menu reveals that the superior, middle, and inferior trunks of the brachial plexus, as well as a portion of the subclavian artery, course through the interscalene triangle. (b) Entries in the pop-up menu system are themselves selectable, and choosing the middle trunk of the brachial plexus links to a representative image and annotation. (c) Graphical annotation browsing may then be used to demonstrate that the middle trunk of the brachial plexus lies superior to the subclavian artery. In this way, the application facilitates exploration of the ontologic and spatial relationships between structures.