I have an externally produced STL file (from a 3D scanner) that I would like to be converted or added to a CT study so it can be used in radiation therapy planning. I’m not sure which of the following ways would work/be best.
Import the STL as a segmentation, add it to an existing CT study, export the entire thing as dicom.
Load the STL and somehow directly export it to a new CT dicom series.
Could someone walk me through how to do one of these approaches?
I can import
You need to load the existing CT study anyway to register the surface scan with the CT, so go with (1).
See instructions for DICOM export here: https://www.slicer.org/wiki/Documentation/Nightly/Modules/DICOM#DICOM_export
How do I register the segmentation to the CT?
There are many options but probably a landmark registration is a good start (SlicerIGT extension, Fiducial Registration Wizard module). You may follow it up with an ICP-based surface registration (SlicerIGT extension, Surface registration module). If surfaces may be deformed then you can use Segment Registration extension to align them with a warping transform.