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Published on Oct 31, 2012
This video shows a technique for unfolding a volume surrounding the bowel wall in the context of the VIGOR++ Project (http://www.vigorpp.eu). Such an unfolding can simplify the visualization of the colon wall using standard techniques and the measurement of the thickness of the bowel wall. Both visualization and measurement benefit from the fact that one coordinate dimension is straight and thus the whole geometry is less involved in the unfolded representation.
The first step of our approach is a segmentation of the inner bowel wall. The resulting surface is a tubular structure whose topology is equivalent to an open cylinder. The second step is to cut this "cylinder" along the shortest path from one end to the other (blue line in video). After this cut, the surface can be mapped to 2D by using a parametrization algorithm like LSCM (least squares conformal map). In the video we show an animation of the unfolding, i.e. mapping to 2D. We employ the original and the unfolded version of the inner bowel wall surface for unfolding the volume that we construct in the next step. The volume is based on positions that are obtained by stepping away from the surface along its normals. After sampling the volumetric MRI data at the positions, we simply transfer it to positions that are obtained by stepping away from the 2D surface along it normals. Thus we have an unfolded volume. Finally, we slice through the unfolded volume to show its structure and fly through the 3D surface.
Video, unfolding and visualization: Alexander Wiebel (ZIB) Data: AMC Amsterdam Segmentation: Robiel Naziroglu (TU Delft)