Institute for Computer Graphics and Vision, Graz University of Technology, Inffeldgasse 16 and Institute of Pathology, Medical University Graz, Auenbruggerplatz 25, 8010 Graz, Austria. caleydo@icg.tugraz.at|Institute for Computer Graphics and Vision, Graz University of Technology, Inffeldgasse 16 and Institute of Pathology, Medical University Graz, Auenbruggerplatz 25, 8010 Graz, Austria. caleydo@icg.tugraz.at|Institute for Computer Graphics and Vision, Graz University of Technology, Inffeldgasse 16 and Institute of Pathology, Medical University Graz, Auenbruggerplatz 25, 8010 Graz, Austria. caleydo@icg.tugraz.at|Institute for Computer Graphics and Vision, Graz University of Technology, Inffeldgasse 16 and Institute of Pathology, Medical University Graz, Auenbruggerplatz 25, 8010 Graz, Austria. caleydo@icg.tugraz.at|Institute for Computer Graphics and Vision, Graz University of Technology, Inffeldgasse 16 and Institute of Pathology, Medical University Graz, Auenbruggerplatz 25, 8010 Graz, Austria. caleydo@icg.tugraz.at