can be evaluated via the segmentation result’s similarity to the ground truth labeling according to the S[ø]{}rensen-Dice coefficient () [@dice1945measures] after each interaction. The interaction data utilized for these segmentations has to be representative in order to generalize the evaluation results.

Types of User Interaction
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As described by Olabarriaga et al. [@olabarriaga2001interaction] as well as Zhao and Xie [@zhao2012interactive], user interactions can be categorized with regards to the type of interface an provides. The following categories are emphasized. (1) A pictorial mask image is the most intuitive form of user input. Humans use this technique when transferring knowledge via a visual medium [@puranik2011scribbles]. The mask overlayed on the visualization of the image to segment consists of structures called scribbles, where $w$ is the width and $h$ is the height of the image $\mathbf{I}$ in pixels. Scribbles are seed points, lines, and complex shapes, each represented as a set of individual seed points. One seed point is a tuple , where describes the position of the seed in image space. The class label of a scribble in a binary segmentation system is represented by . Scribbles need to be defined by the user in order to act as a representative 