Liver tumor alignement

Hello,
I study liver tumors in different scan series and I am trying to compare their size, centroïds…
Hence, I’m trying to do a segmentation on four volumes :

  • CT scintigraphy and CT PET where I contour the liver
  • scintigraphy and PET where I contour the tumor

The problem is that the tumor of TEP is not aligned with the CT, and same for the scintigraphy. Why don’t the tumors directly imbricate in the livers and how can I proceed to fix this?
Thank you in advance