Converting MRtrix connectome model to .stl for 3D printing

Hi, I created a whole brain connectome in MRtrix, which I converted to a .vtk file. I can open the file in Slicer, but when I save it as an .stl file, that file seems to be corrupted as I can’t open it with any software (meshlab, paraview…). Is there an easy way to export fiber bundles as stl or obj files for 3D printing?

Cheers, Lena

You may use these code snippets to export scene content to STL: