My 3D model has a smaller 3D model inside of it???

Operating system: macOS Catalina 10.15.7
Slicer version: 4.11 20200930
Expected behavior: I have very very carefully drawn the circumference of the aorta in green to be as precise as possible. When I click “show 3D” in segment editor, I expect to see 1 hollow aorta with a very precise radius.
Actual behavior: There is a smaller 3D aorta inside my aorta… I don’t understand… You can see in my images that the thickness of the aorta shell is literally a single pixel (as can be seen in the “frontal view on the bottom left”)… As I move my cursor to each side of the shell (again, as seen in the “frontal view” on the bottom left), we can clearly see that my cursor is passing through 2 different shells in the 3D view…

There is literally a smaller version of my aorta inside the bigger one… How is this possible? Can I get rid of it? Have I done a mistake?? 3DSlicer doesn’t seem to recognise that there are 2 aortas in either the frontal, saggital or axial view… It only sees this in 3D view…

Please watch my images in order to see how my cursor touches 2 aortas in 3D view when it is clearly only touching 1 aorta in the frontal view.

PS: I am using MRI images with a low resolution of 1.7 mm per pixel.

Segmentations are always considered as volumes, so the surfaces you see are the different sides of what you can think of as the vessel wall. Because of the MRI pixel sizes, it’s thicker and more bumpy than a real vessel wall.


Thank you that is very reassuring, I see what you mean.