by $\mathbf{p}^n_1$ and $\mathbf{p}^n_2$, is zoomed in for the option view on the right and displayed as a cyan rectangle in the overview image on the left of the . The differences regarding the previous iteration’s contour line and one of the four new options each are highlighted by dotted areas in the four overlay mask images. After the user selects one of the labelings, the two new seed points are added to the current set of scribbles $\mathbf{S}^n$. The scribbles are utilized as input for the next iteration, on which basis two new locations are computed.

The system-defined locations of the additional seed points can be determined by , the location(s) with maximum number of label changes during segmentation. Frequent changes define specific image elements and areas in which the algorithm indicates uncertainty in finding the correct labels. Two locations in $\mathbf{h}^{t=\infty,{n-1}}$ are then selected as $\mathbf{p}^n_1$ and $\mathbf{p}^n_2$, which stated the most changes in labeling during the previous segmentation with input image $\mathbf{I}$ and seeds $\mathbf{S}^{n - 1}$.

![Guided segmentation prototype user interface. The current segmentation displayed on the upper left can be improved by choosing one of the four segmentation alternatives displayed on the right. The user 