I am working with CT data that have been acquired from the same patients at different time points. My aim is to evaluate the tumor shrinkage (I have established it well in the 3D slicer, and works well) and tumor’s movement (this part is the question).
Since I am working on the lung (which has breathing phases, and I use average CT), the determination of the tumor’s movement is challanging. I plan to use a coordinate system in which I will assign the XYZ axis by taking advantage of the human anatomy to determine coordinates for each time point.
When you have both patient motion (breathing, body posture etc) and pathological changes (tumor growth, atrophy etc) it can be very difficult to untangle what’s really going on. Probably your best quantifications will be relative, such as distance from one side of the tumor to the other or distance from tumor to well defined anatomical landmarks. You can do these measurements in 3D with Slicer Markups or calculate size and other features with the Segment Editor and Segment Statistics or SlicerRadiomics.