Mechanical Hardware Affects on CT Scan & Stl File

[Envision 3D Printing]

I used democratiz3D to convert a clients spine CT scan into an stl and then a 3D print.  I evaluated with high res and then paid for premium. The results were great.  Now the same client wants another model of his spine but this time it is after his surgery which included  replacing 3 of his discs.  This time the stl file does not look so good.  I am evaluating the high res at this time. There are a lot of artifacts around the surgical area which I am assuming are due to the metal hardware causing higher reflections in the CT scan.  Is there any settings/options that democratiz3D has that can help this issue?  Will the premium stl resove the issue? 

 

 

 

 

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[Dr. Mike]

Dear Envision,

 

Thanks for being a great member. The problem isn't with democratiz3D but rather the CT scan. Actually it isn't the CT scan really either, but the metal in the patient's back. You see, the x-rays cannot penetrate the metal implants at all, so the CT detector interprets this as a dense, star-like pattern that is called beam hardening artifact. It is a common artifact in CT scans where patients have metal implants. Although there are some experimental research algorithms that when run at the time of the scan can remove these artifacts, they need to be on the actual scanner. Most CT scanners do not have this type of artifact correction. My tutorial on how to choose a good CT scan for 3D printing has a section on this called Imaging Artifact. Take a look and you will see what I mean.

 

When the scan with the artifact is plugged into democratiz3D, the artifact is reproduced as well. Democratiz3D doesn't know what is artifact and what is bone. Other than getting a scan without the artifact, the only other options are to manually edit the mesh and remove the artifact, or live with it and understand that it represents artifact and not real anatomy. I know this isn't ideal but it is the limit of the technology today.

 

Hope this helps.

 

Dr. Mike