Hi Joerg,
there are ways to bring polygonal data into MoI, but those are, as far as i know, only commercial options available.
The most elegant in your case would be to buy an edu vers. of 3DCoat and (auto)retopo the scanned mesh to obtain a quad dominant polygon mesh, which then could be brought into Rhino/T-Splines(demos) and then processed inside there to obtain a perfect NURBS object of the model.
The second method is not as elegant, but i tried to do something similiar in Shade 3D with 2 Python Scripts to get a shaded mesh which then saved as IGES file in Shade, to bring into MoI. As a test i used a non-frozen SubD mesh from modo, to get this result:
|