Aorta coarctation segmentation

as a correctness I want first to introduce myself to the community
I am a italian technographer of hemodynamics
I do not have the right skills but I have to convert a study ct into a stl file for printing the preoperative model. I have already performed a segmentation but the results are approximate and not transferable in the operative field. I would need a tutorial that allows me to complete the project with a complete stl file with the blood mold and the inside of the aorta with the pathology of the coarctation, empty and transparent, so that I can follow the course of the catheter. sorry if I posted here if there is a discussion in the medical field I would be happy to move
Best regards

Francesco ,TSRM

Have you completed these segmentation tutorials yet?

https://www.slicer.org/wiki/Documentation/Nightly/Training#Slicer4_Image_Segmentation

I would suggest to try “Grow from seeds” effect.

You can create a hollow vessel model by copying the blood segment, expanding using Margin effect, and subtracting the blood segment using Logical operators effect.

If segmentation quality is not good enough (not smooth, etc.) then post screenshots and we can give more specific advice.