Interactive live-wire boundary extraction.

Live-wire segmentation is a new interactive tool for efficient, accurate and reproducible boundary extraction which requires minimal user input with a mouse. Optimal boundaries are computed and selected at interactive rates as the user moves the mouse starting from a manually specified seed point. When the mouse position comes into the proximity of an object edge, a 'live-wire' boundary snaps to, and wraps around the object of interest. The input of a new seed point 'freezes' the selected boundary segment and the process is repeated until the boundary is complete. Two novel enhancements to the basic live-wire methodology include boundary cooling and on-the-fly training. Data-driven boundary cooling generates seed points automatically and further reduces user input. On-the-fly training adapts the dynamic boundary to edges of current interest. Using the live-wire technique, boundaries are extracted in one-fifth of the time required for manual tracing, but with 4.4 times greater accuracy and 4.8 times greater reproducibility. In particular, interobserver reproducibility using the live-wire tool is 3.8 times greater than intraobserver reproducibility using manual tracing.