[1] Ulm Univ Appl Sci THU, Inst Comp Sci, Ulm, Germany
[2] German Canc Res Ctr, Dept Comp Assisted Med Intervent, Heidelberg, Germany
[3] Swiss Fed Inst Technol, Dept Informat Technol & Elect Engn, Zurich, Switzerland
[4] Uppsala Univ, Dept Informat Technol, Uppsala, Sweden