I have a 3D geometry of an organ with a cavity. I have it in both NRRD and STL formats. I cannot disclose the data due to ethics, however, I can give a real world object that presents a similar issue. Please find the below image:
As you can see there are two surfaces; inner and outer. However these two are connected in the sides. (image below)
How can I separate the inner and outer surface of these kind of structures, without manually selecting the faces one by one and deleting them?